It's important to remember that the Dodson WAS more expensive than the Bryston. Recall that the DA217 mkII-D is an older DAC (I think it came out in Fall 2000). Accordingly, as of right now, the Dodson appears to be very close in price to the BDA-1, and probably lower in most cases. However, if the DACs were currently trading at their original MSRPs, then no I don't think I would say that the upgrade would be worth the 2.5x price difference. At a couple hundred bucks, it's a different story. However, one also needs to take into account the fact that Dodson is now defunct, though still supported, and the gear is getting old. While built well, it ain't gonna last forever.
As for diminishing returns, it seems to me that you can get a very, very good DAC for $1500 or less (much less in some cases) on the used market. After that, it seems to me (without much support for the following conclusion) that the next "rung" probably starts at $2500, but that's speculative at best.
Thank you, those are all very good points. I guess i'm at a point where i'm trying to figure out what is the best way to spend $2K on a DAC...