Never cheap, business travel is suddenly getting even costlier. And these days, the pressure is really on for business travelers to control their expenses, particularly such big-ticket items as air fares and lodging.

As a result, more business travelers than ever are checking into mid-priced and budget hotels. After all, the average room rate nationally is now topping $56 -- and many big-city hotel rooms are $150-plus a night. So hotel rooms that cost $40 or less have an obvious appeal for cost-conscious travelers and travel planners. In fact, a recent survey, commissioned by the Marriott Business Travel Institute and paid for by the American Express Co., showed that about 36 percent of frequent business travelers are staying in either moderately priced hotels or economy hotels and motels.

These lower-priced facilities are competing effectively with full-service, upscale hotels by offering services specially tailored to the business traveler -- but at economy prices. For example:

Budgetel Inns. Since February, Budgetel has been serving a free continental breakfast to all guests -- delivered right to their rooms. Coffee, juice and a Danish are served before 7 a.m. on weekdays -- a convenient time-saver if you're in a hurry to make a meeting.

Other features aimed at business travelers in Budgetel's 72 inns include complimentary local telephone calls; free fax service (guests pay only the long-distance phone charges); desks and extra-long beds in every room; and, upon request, the use of an executive conference room. Some of these amenities, as business travelers well know, are not available at higher-priced hotels. And at Budgetel, it's all available for about $34 a night.

Hampton Inns. With rooms that average $44 per night nationally, the economy Hampton chain has increased its share of business-travel bookings by more than 10 percent since 1988, according to Ray Schultz, president of Hampton Inns Inc.

All 200-plus Hampton hotels offer a free continental breakfast in the hotel lobby and free in-room movies; most have hospitality suites for meetings, fax machines and free transportation to local airports; and many have swimming pools, exercise equipment and hot tubs.

Frequent business guests can also save time by filling out a travel profile that permanently enters pertinent booking information into the hotel's computer, facilitating the registration process the next time you stay there.

Fairfield Inns. Part of the Marriott Lodging group, the Fairfield Inns chain began adding fax machines to all 45 of its facilities last summer. Most rooms, which average $30 to $45 a night, feature a king-size bed or two double beds, a large desk and well-lit work area and a comfortable chair and ottoman. The telephone has a cord long enough to reach both the nightstand and the desk, local calls are free and small meeting rooms are available. Complimentary coffee and tea are available in the lobby each morning. Also standard: an outdoor pool and a vending machine area. And, new this summer, the economy chain has added another service of special interest to business guests: same-day dry cleaning.

Red Roof Inns. This Ohio-based economy motel chain was cited in 1988 by the staff of Business Traveler's Letter, a Runzheimer International publication, as providing the best services for business travelers among budget-priced motels.

Red Roof guests can, for example, fax up to five pages for just $2.50, while some full-service hotels may charge as much as $20 for five pages. Red Roof guests also may receive up to five pages of faxed material free (and pay 50 cents per page thereafter) and use copy machines in the lobby for a minimal cost. Room rates run about $37.50 a night.

The motel chain's new "Business King" rooms provide a large, lighted desk area; touch-tone telephones with modem jacks for computers; king-size beds; a free daily newspaper and morning coffee.

Bed-and-breakfast bargains. More business travelers are checking into B&Bs, in part because of cost concerns but also to escape the anonymity and loneliness of hotel rooms. The B&B option is becoming increasingly popular in large cities, where travelers can find comfortable lodgings that range from $30 to $75 a night.

If you're going to be conducting business with the home office or churning out a report on your computer, B&Bs may not be best for you. But if you're headed to New York or Chicago for a business meeting, a B&B might offer ambiance and some company, at a good price.

The National Bed & Breakfast Association (203-847-6196) in Norwalk, Conn., publishes several guidebooks with listings of B&Bs by regions.

An airport bargain. Honolulu International has a solution for that next L-O-N-G layover: the Shower Tree, a shower and sleep facility on the second floor of the main terminal. A bed rents for $4 an hour; a bed and shower run $7.50 an hour. Pay $22.75 and the bed and shower are yours for eight hours. Almost any airport -- especially with today's frequent delays and missed connections -- would befriend passengers by offering this kind of facility.

Expense Accounts Despite the rising costs of getting there and staying there, a new survey shows that, so far at least, individual travelers have managed to hold the line on most expenses. Runzheimer International's biennial analysis of domestic and international business travel found the annual cost per traveler has actually decreased, from $6,727 in 1988 to $6,250, based on the first half of 1990.

Travelers and travel managers have been able to reduce expenses by aggressively going after the lowest air fares and by negotiating lower rates for car rentals and lodgings. Also, according to Runzheimer, a travel management consulting firm, travelers have saved money by consolidating individual trips and getting the same amount of business conducted in fewer out-of-town outings.

That's the good news. The bad news, also from Runzheimer, is that rising air fares, room rates, hotel-room taxes and restaurant bills are expected to push overall travel costs up another 8.1 percent next year, making cost-cutting measures all the more important.

Business Bonuses American Express has opened a business center -- with work cubicles, copy and fax machines, an IBM computer and telephones -- in the main terminal of Philadelphia's airport. Located in the main terminal between Concourse B and Concourse C, it is available to card holders or American Express travel agency clients.

The Hertz rental car company has expanded its popular Hertz Travel Guides to include the cities of San Diego, Boston, Detroit, Seattle, San Antonio/Austin, Phoenix/Tucson, St. Louis and Portland, Ore. These and other free pocket-size city directories, which are updated quarterly, feature fold-out color maps, a brief history of the local area and listings of local dining, shopping and entertainment possibilities.

Amtrak is now accepting Discover credit cards for all services. The Discover card (for which card holders pay no annual fee and sometimes receive small rebates on purchases) joins seven other cards -- American Express, Carte Blanche, Diners Club, MasterCard, Visa, Air Travel and the Japan Credit Bureau -- that can be used as payment at Amtrak train stations, self-service ticketing machines, travel centers and dining cars.

Sign of the Times Radisson Hotels International Inc. will open the first American-managed hotel and business complex in the Soviet Union this December. The 535-room complex, including 165 business suites, will be located in downtown Moscow on the banks of the Moscow River and near the Kiev Railway Station.

The Radisson Slavjanskaya Hotel and Business Center will have four American restaurants, extensive meeting facilities, Western-style hotel rooms and a health club. Among its more sophisticated business services will be direct-dial telephones in each room or business suite with worldwide dialing capabilities.