Celo, we each have our own experiences and I'm not trying to discount yours, I've just had a dissimilar experience.
I'm able to hear differences in similar priced gear. I've owned 6 different DAC's in the sub $1000 range and I've yet to hear two that sound the same -- different sound stage depths, different widths, different abilities to render details or nuances in music, different abilities to replicate wooden percussion instruments, etc.
Sometimes I find very dramatic differences, i.e. Audio GD vs Denefrips Ares. I also hear differences in DS vs R2R, preferring R2R by a wide margin.
I have friends and family (wife has golden ears) that hear the same differences I hear.
My point is that some people do hear differences and price doesn't necessarily matter. Two of my favorite DACs I own right now happen to be the lowest priced.