10ml Salts are highly regulated , need tox testing, cleanroom manufacturing and registering with the MHRA etc which is quite a long and expensive process.
The shortfill market has a low barrier of entry, they're pretty much unregulated, anyone can open a facebook page, mix them up in a bathtub and slap a fancy label on it..
(which many companies are trying to compete on price with)..
The shortfill market is massively saturated, to the point it wouldn't surprise me if someone starts selling them for a £1 a bottle soon.. We've seen £2 recently!
Personally, I'm hoping the new regulations will allow us to produce nic ready products in larger bottles.