Ack stainless steel is making a comeback? No thanks. The days of toting around a 4 pound hunk of stainless attached to a 3 pound tank are over. However I do remember the first apocalypse reg I got was used and cost me about 300 bucks in 1998. I sent it to AA in which they set it up for the ultra modern 4500 upgrade for 160 bucks with tank. That was awesome. I had it on my mag for a few years until the preset screw in regs were tested reliable. I still was able to sell it for a pretty descent amount.
If memory serves me correct, the original HPA systems were good for the cockers, mags and first E guns hitting the market at the time. I think some of it still has decent flow but it is easier to have one tank for multiple guns without needing to have multiple cradles. However, I do remember Tom Kaye was telling a group of us that AA regs were much slower on the recharge than what the Flatlines were capable of. This was about 12 years ago when Flatlines came out.