People can pay $100 if they want, but better deals are out there. Note the last two GunBroker links, they are for the same mag with a nice little profit for the re-seller (last link). Incidentally, two of these auctions are ones I won, including a $25 SEY that is like new and a $19 J that is on its way.
There were some $65-85 auctions for USGI 30-rounders on GB too and I noticed a 30-rounder priced at $100 that just doesn't seem to sell no matter how many times the dude puts it back on the block.
http://www.gunbroker.com/Auction/Vie...Item=154630682
http://www.gunbroker.com/Auction/Vie...Item=164638393
http://www.gunbroker.com/Auction/Vie...Item=162833440
http://www.gunbroker.com/Auction/Vie...Item=162873815
http://www.gunbroker.com/Auction/Vie...Item=159817798
http://www.gunbroker.com/Auction/Vie...Item=162565247
http://www.gunbroker.com/Auction/Vie...Item=164356278
http://www.gunbroker.com/Auction/Vie...Item=162556932
http://www.gunbroker.com/Auction/Vie...Item=163357478