Salesman and folks who have already been sold, will loudly sing the praises of plugging a computer into your very own home. Think of the opportunity for better bookkeeping, they will tell you. Think of educational programs and video games.

Then think of the cost.

The basic bare-brained personal home-computer system starts at $450. And for that price all you get is the keyboard and one cartridge to work with.

If you want to store your grocery list, play chess or keep your checkbook balanced, be prepared to write some big checks.

You can't get modems, printers, interface and joysticks without spending at least a couple of thousand dollars. A truly addicted computerite can spend $10,000 on a system and still not feel completely wired.

Before buying into this new electronic age, you can test-spin, punch or program a dazzling variety of computers at more than a dozen area showrooms.

Salesmen report the lunch hour crowd is thick with non-paying players. And all are welcome. "If they play long enough, they usually end up buying something," said one salesman. THE MATH BOX, 4431 Lehigh Road, College Park, 227-6228; 2627 University Boulevard, Wheaton, 933-6555; 9650 Main Street, Fair City Mall, Fairfax, 978-5400; 2109 L Street NW, 463-7474. CHARTZ ELECTRONICS, 856 Rockville Pike, Rockville. 301/340-0200. BIT WIT, 7801 Old Branch Avenue, Clinton, Maryland. 301/868-0005. Computer AGE, 9433 Georgia Ave, Silver Spring. 588-6565. COMPUTER CROSSROADS, 9143 Red Branch Road, Columbia. 310/730-5513. PROGRAM STORE, 4200 Wisconsin Avenue, NW. 337-4691. COMPUTERS, ETC., 9330 Georgia Avenue, Silver Spring. 588-3748.

COMPUTERLAND/TYSONS CORNER, 8411 Old Courthouse Road at Route 123. 893-0424. COMPUTERLAND/ANNAPOLIS, West Street and Route 2, Annapolis. 301/266-6277. COMPUTELAND, 16065 Frederick Road, Rockville. 301/948-7676. COMPUTERS, PLUS, 6120 Franconia Road, Alexandria. 971-1996.