Better DAC topology, better power supplies, better clocks, better components, better pre and post analog stages and better input types all have a huge impact on what we universally call a DAC. It could be true that all digital to analog converters sound similar (not the same) but that all the other factors mentioned above make up the huge differences in DACs
A digital to audio converter can be a tiny single chip but a DAC is a combination of far too many ancillary variables to be generalized.
And, yes, the price of the DAC - not so much the "converter" makes for better sub-sytems and better sound.