Any bike from 91... Expect about 25 bucks... maybe.
Technology, especially in BMX has changed. Everything is now U-Brakes, cantilevers, and 1 1/8" head tubes. The early 90's was especially painful for bmx bikes when Standard Industries came along and rewrote the book on what a quality bmx bike could be.
There are some top of the line frames from the late 80's and early 90's that are simply worthless by today's standards because their geometry, build quality, and design elements simply don't even compare to $100.00 complete bikes at Wal-Mart. Let alone an entry level Haro or DK.
Man, I hate saying stuff like that, but it is the reality. You might have better luck on eBay than in the classifieds or something. But, if the frame is high quality, but isn's a complete bike, then kids will be better off buying a newer design.