Fun fact, most interfaces probably use the same half-dozen DAC chips. You have Analog Devices, AKM, Burr-Brown (which I never hear about anymore), Texas Instruments, or maybe a THX chip to choose from. You buy the chip from them, get the implementation documents (which basically tell you what voltages power it and which pins to connect which signals to) from them, and then slot it into your design.
I know this from a company called Schiit in their hifi dacs. The $100 Modi uses an Analog Devices 4490, which (until recently) was the same DAC in their $400 Bitfrost, and the same in their $700 Gungnir. What changes is the power supply quality and clock quality feeding the DAC to lower noisefloor and jitter, but the actual piece doing the work is the same across most devices. Same goes for audio interfaces and probably the A/D Converter side as well. I pay attention to I/O and drivers above all on the interface, and know that the price is driven by the software and how well the off-the-shelf hardware is implemented.
That’s not to say the implementation of those A/Ds and D/As isn’t important, those same half dozen chips power 99% of the dozens of audiophile DACs out there and companies do get different results with their various implementations. And absolutely you can get into bespoke DAC designs, for $2000 and up. Not sure where bespoke A/D starts, but last I heard it was the size of a refrigerator and if you have to ask you couldn’t afford it.
And then you have RME doing stuff with FPGAs and Universal Audio adding SHARC dsp for real time plugin acceleration, and I’m sure there’s other differentiators out there too. That stuff is really cool, even if I’d probably never use it.