And I picked up one from a $4 bin at a show in January. It was the only one left. That, like the ones you found, was what I would classify as a "pricing mistake". Silver proof quarters do not "hit around $2.50 - $3 raw" today. They "hit" bullion value, which is currently well north of $7. If you find them for significantly less, buy all you can, and resell them at a profit -- but don't assume that "the going rate" is less than melt value.
Also, spot's jumped quite a bit since january. I don't know what exactly it was at in Jan., but it's over $40 now. A 1961 proof quarter at $7.50 is a decent price, even if graded by IGS. Crack it out, get it slabbed PR-65 or less by somebody else, or (better yet), leave it raw or in that IGS slab and remember it's not a PR-69.