Bad enough that a simple little Rembrandt will set you back at least $3 million. Have you priced frames for your artworks lately?

True, not everyone can hang the Master's "Portrait of Juno" over the mantel. But even the simplest of posters, the fondest of photographs, looks better in a frame.

For the penurious collector who shuns the standard assemble-it-yourself chrome frame as boring and unoriginal, there is an alternative to costly custom frames. Scattered around the area are a growing numbeer of frame-it-yourself operations. These outfits, frequently tucked unobtrusively in suburban shopping centers, offer a selection of mouldings, glass and matting; work space and materials and - most important - supervised instruction.

Custom frame jobs for the average eight-by-ten print, including matting, backing glass and moulding, can run anywhere from $20 for the barest, most basic black frame, to $75-$100 for a more elaborate effort. By framing it yourself, you can expect a range of $8 to $15-$20.

For the less adventurous, many department stores sell art supplies, including premade frames, matting and glass. But the savings here will not equal the do-it-yourself approach.

Do-it-yourself frames, of course, are not without their drawbacks. There is, first of all, the very real danger that the novice framer will accidentally damage his irreplaceable work of art. Even a misplaced drop of glue can be disastrous. Any do-it-yourself project takes time: Plan to spend several hours for your first effort; maybe a little less the second time. And what with epoxy glue, sawdust and the like, the work can be messy, so wear grubbies.

One custom frame merchant carped that his do-it-yourself competitors offer a limited selection of mouldings. But a visit to the do-it-yourself outfit revealed a wall full of mouldings - surely an adequate selection for anyone who will settle for a self-made frame.

So where does the aspiring artisan head for his frame-up? Some suggestions:

A Gallery Shop. A custom frame shop and print gallery that also sells do-it-yourself material. Locations at 1753 Connecticut Ave. NW; 4232 Howard Ave. in Kensington; 8649 Colesville Rd., Silver Spring.

American Art Make-a-Frame. Four suburban locations offer an extensive selection of framing materials, classes or on-the-spot instructions, and ample work space: 11770 Parklawn Dr., Rockville; Little Falls Mall on Sangamore Road in Bethesda; Shady Grove Center, 15948 Shady Grove Rd., Gaithersburg; 3519 S. Jefferson St., Bailey's Crossroads, Va.

Brown's Imperial Framing Studio, 8641 Colesville Rd., Silver Spring, sells framing materials and offers instructions.

The Frame Factory, 7130 Little River Turnpike, Annandale, will sell materials necessary for framing, but provides no workspace.

Framecraft, at 1075 Seven Locks Rd. in Rockville, specializes in framing supplies for needlework. Instruction and work space are provided.

Frames By You. Do-it-yourself framing, including instruction and work space, at 521 Maple Ave., Vienna, Va.

Frame-It-Yourself, as the name implies, caters to the do-it-yourselfer with materials, work space and instruction. For repeated framers, the shop gives a discount card good for each work after the first frame job. 8700 Richmond Highway, Alexandris.

Venus Art Frame Plastics has framing materials and work space for the do-it-yourselfer amidst others crafts supplies at 5216 Wilson Blvd., Arlington.