Donated?
Back when those were built many members donated parts for members builds. Especially college kids and newbies. Not 601 furniture, barrels or BCG's but bolt catches, many circle buttons, mottled pgs, grey slip rings etc. I have seen some 601 furniture given away though. Saw a lot more re-profiled lowers back then also. Then NDS started saving people lots of work, repro parts started popping up and prices escalated.
When I first started viewing retroland approx 06-07 anyone who paid more than $250 for a surplus upper needed their head examined. Gunnyssurplus and OOW had quite a few for $275ish excellent and $250ish for good condition and basically no takers for at least 6 months do to exorbitant pricing besides the VMP and MP stamped pieces. By 08 it was on. Parts started drying up and supply/demand /greed kicked in. Local fireman built complete retro rifles on PAWish lowers and sold them for a small profit at $399 less mag and sling, really before retroland had surfaced and parts were basically free. In my area AR15.com was one of the biggest jokes on the web in the AR community. Funshows still had tons of parts and if one couldn't afford a Colt they built a retro out of Colt parts for 1/4 of the cost.
Retroland and it's founding members helped change the whole outlook of the site as it added a little class and comradery and not just a mine is better and yours blows scene. If one sold import parts they were almost run off. Now selling knock offs is kinda standard and giving up parts equal to those taken is a pretty rare thing.