TO THE ORGANIZED elderly and handicapped people around the country, the federally mandated, yet-to-materialize Transbus has become an important symbol of dignity, a dream vehicle in a perfect world of low-floored public transportation. But for all Americans, there's a tough question of hard economics: Are people willing to pay perhaps $250,000 a bus for this model, or will the handicapped have to settle for something less?

Transportation Secretary Brock Adams, who ordered that all buses financed with federal aid after this fall be Transbuses, got a taste of the answer this week: No manufacturers bid on the first order of Transbuses for Philadelphia, Miami and Los Angeles. American bus manufacturers had announced earlier that the federal specifications for the buses made bidding impossible; and foreign manufacturers failed to answer the call.

So far, development of the Transbus project has cost an estimated $27 million; the $250,000-a-bus price tag is an industry estimate. Though the costs and specifications are to be re-examined (as they should be, to clarify any doubts about the industry's response), authorities should look at more modest alternatives. Since 1977, all buses built have been made for ready addition of wheelchair lifts. In the Washington area, for example, hundreds of these buses have been purchased and tests are under way on regular routes. A standard bus complete with lift sells for about $120,000.

Many of the lobby groups for the elderly and handicapped are dissatisfied with these lift-equipped buses, however. For one thing, the organizations says, the lift equipment so far has a tendency to break down. But far more important, they argue, is the matter of rights and dignity-the handicapped do not seek special treatment or "separate-but-equal" access to public transportation. Certainly society should strive to make the daily living of disabled people as much like that of others as possible. But there are differences to be recognized and compromises to be struck-and Transbus is a case in point.