I hate to say it, but I'm not shocked by those high prices for Gen 1 PMAGs. Somehow they've turned into collectibles, despite having been produced by the thousands. I have a few black Gen 1 non-window mags that I've barely used, including some that I've never used, back when they came in a ziploc bag. I didn't really trust the idea of polymer mags back then, and I thought the window mags might be more prone to failure, so I avoided them. I found three new black 20-rd Gen 1 mags a few years ago for $20 ea that I bought just for fun, since they were already going for $25-$30 at the time. I also bought a like-new 30-rd OD green Gen 1 last year for $18 shipped off that big auction website - it was listed as a 10-rd mag, but the photo clearly showed a 30. By the time I received it, the auction site had removed the listing.
They're interesting to me as part of the history of Magpul's product line, but I'd never pay the collector prices people are asking for these days.