I don't think that's really a fair statement. I never said anything about the overall cost needing to be lower. I only said it was already an expensive device (which it is; greater than half the cost of my 11.2 AVR) and that I'd be willing to pay EVEN MORE if it meant I could keep my bass management and room correction system active. Pardon me for wanting to keep +/- 2.5dB overall frequency response (with room correction) instead of +/- 5dB without it. Trying to get the room response to that level of precision with room treatments alone would be an exercise in frustration. Getting flat 20Hz bass response without a subwoofer and correction would at the very least entail replacing the main speakers with larger towers at considerable cost as well.
I wasn't implying a converter had to be included in the SM. I'd be perfectly happy with a 3rd party analog-to-digital converter. There are 2-channel + video versions galore out there, but 5.1 analog surround is obviously too much of a niche so they didn't bother including it in their designs. Most people are trying to go the other way around (DAC). I didn't realize reporting my attempts to locate an external analog to digital converter was offensive to people. The shortcoming is the receiver which does not digitize the analog inputs so that its own vast processing (from Audyssey to surround modes) can be applied. I know of a couple of AVRs that did offer that option, but that was some time ago and they were high-end products.
Whether the SM device itself is worth it to me in the end or not will depend on what it does for 2-channel stereo music. I haven't found surround modes for 2-channel to be convincing thus far (meaning Dolby Surround or DTS modes used with 2-channel music in particular), but the raves about this product has me willing to buy/try one, but that doesn't mean I welcome the implied criticisms for simply looking for a way to keep bass management and Audyssey working, even if with an external ADC device.
The fact most of the systems I've seen in use with this device look more like the 1970s than the 2020s implies perhaps I'm simply the wrong customer in general. I don't currently own any 1970s Quad LPs to play (not that I wouldn't be interested in trying some). I'm simply looking for a surround mode for music specifically that is more interesting than Dolby Pro Logic IIx or DSU, neither of which I found very interesting for most music as the separation is poor at best while dismantling the traditional soundstage (a half effort at best between true discrete and traditional stereo). My feeling is that if you're going to move things into the surround speakers, actually move them rather than "blur" them half-way, which is often what I feel Dolby does to 2-channel music unless the music has very strong out-of-phase material in it. Most of the reviews of SM suggested far more envelopment than something like PLIIx, which is what piqued my interest in the device. DSU is worse than PLIIx for 2-channel music, IMO. DSU and Neural X are excellent for upgrading 5.1 music a bit further, IMO so clearly if the SM works extremely well, it'd be interesting to see what height expansion could possibly add (maybe nothing at all, but that's just my curiosity, but it won't work with the analog input mode either).