Just because m400 has the same 4499 as d90 it doesnt mean they compete at the same price point... sp200 doesnt compete at the same price range with Benchmark hpa4 just because thy both have flagship thx aaa 888 chip inside, there are other components that measure up to the price. if smsl released m400 at the same price as d90 it would be doa... could also fint d90 at 600 when it was first released
Its the targeted audience that matters.
Clearly, the D90 sells quite reasonably well at its price point. The M400 has almost identical specifications and based on their own published AP measurement results, measures at least as good as the D90.
And what's the D90 MQA's MSRP again ... ?
Manufacturers will sell their products at whatever their target audience will accept. Clearly there is a market for the D90 (and maybe D90 MQA) , so there is clearly a market for an SMSL DAC at that pricepoint for that kind of published performance too.
Audio transparency wise, the M200 and M300 are clearly beyond audible transparency. And they are clearly in the low US$200/pc range, which I think is the market segment you are looking at. The former having a build-in power supply, the latter having a separate power brick. Almost identical performance and features. Well worth a look if you are only willing to spend in that ballpark.