A combination of how many people report using them on forums and how often I see customers of my profiling business using them.
Got any better insight ?
No, but that doesn't make your figures more reliable as a result.
This printer is cheaper, smaller and targeted at a different level of consumer - most of whom probably have no knowledge of profiling or have decided they have no need. I think it's a mistake to compare it to other Pro level printers and expect that you'll see a proportionate fraction through your business.
The cost of custom profiles versus the cost of the underlying hardware, for example, would have an effect, let alone (as mentioned above) the difference in basic customer profile.
I want to repeat that I'm in no way suggesting it shouldn't be discussed or that there shouldn't be any concerns, I'm just suggesting that, as always, it's better not to make assumptions but rather to simply acknowledge where there are holes in our understanding.