No, because the D3 does not have a line output--it can't be used as a standalone DAC for non-headphone systems.
R&D of parts, manufacturing cost of parts, labor cost of parts, marketing cost of parts, R&D of the DAC, parts cost of the DAC, labor cost of the DAC, marketing cost of the DAC.
It would be a very simple process except we're dealing with:
1. A finite amount of samples that need an infinite amount of interpolation.
2. Time constraints (i.e. work must be done before the next sample arrives).
44,100 samples per second only approximates the original waveform. It's up to the DAC to guess how to smooth it out. Keeping the timing accurate is difficult because clocking isn't always accurate--this is called jitter. The quality of parts varies in every section of a DAC: DAC chip, power supply construction, wire fault tolerances, etc., etc.
So, it's not simple.
But you may be on to something -- in another thread "Bel Canto USB Link SPDIF" we talk about a USB-Coax adapter (like the Empirical Freeway, Off-ramp) that claim to address timing, and other items so I wondered if you had one of these could you use an "inexpensive" DAC and have still superb music since the DAC no longer needs to worry about timing and some other elements.
I know it's not that simple.