I have been using Mojo with IEMs from about $200-1000. To me, the contribution of Mojo to the sound quality I get is way higher. There is an underlying musicality that I find simply engaging, which is hard to put in words. It just keeps me interested in the music.
I tried other DACs but kept returning to the Mojo.
I also asked myself many times what I would want to buy/keep if my budget was limited to say $700 or 1000, and I would seriously prefer my $200 JVC FDX1 with Mojo over my $1000 Sony IER-M9 without. But this is a deeply personal choice, and I guess most listeners would decide differently.
I think it has something to do with my classical music experience of listening to many live concerts and playing the piano. I am really irritated when acoustic music does not sound right. The Mojo was really a revelation in that sense.
Hugo 2 is significantly better in terms of staging and especially note definition and precision top to bottom, but the Mojo is a bit like a really old recording of great music - not technically perfect but it captures the soul of the music beautifully. $500 is a lot of money for many, but if you love music and it‘s within your budget I think it‘s a great investment.