Spice was a big problem in the UK, particularly in the homeless population just around the time it was banned, and for a year or so after each of the subsequent variants got banned, until eventually all of them did, in the one fell swoop of the NPS Act in 2016. The vendors were virtually giving these substances away in last minute fire sales as the ban dates loomed, and they clearly had huge bulk that they had not shifted.
These drugs were never very popular amongst most recreational users, as they tended to be unpleasantly fierce, and unpredictably strong. However, it seems logical to assume that a number of dealers or criminal gangs took advantage of the availability of the substances at ridiculously cheap prices for kilos of the stuff. They ended up finding a market for these drugs among the homeless populations who could get utterly annihilated for hours at a time, for very little cost.
These substances were also available throughout Europe, in the mid 2010s, but I don't know if the same things happened to the same extent that it did in the UK, in other European countries.
The spice variants were also available in the USA, but I really don't know how much they did or did not gain any traction, amongst different populations.
I do recall that there were lots of threads about spice, and all of it's subsequent variations on EADD and other sections of bluelight back in the day. Many posts were from USA users IIRC. Not sure how representative that might have been of the bigger picture of what was happening over there. Obviously the USA has a much larger population than the UK, so there were bound to be more posts from American users, although of course that doesn't necessarily mean that a greater proportion of the population was using these things,.
I think the spice variants would probably take the crown for the cheapest drug of all time. At prices something like £5 per kilo for the pure powders.. (I cant remember exactly, but it was certainly incredibly cheap.) And a little of that stuff would go a very long way. Just dissolved in acetone and sprayed onto plant matter, or weed, there'd have been thousands of little bags of that stuff produced for next to zero cost. The acetone would evaporate, leaving the plant matter coated in spice, often very unevenly, leading to 'hotspots' in the bags, that would take people's heads off. As we saw.