Supply and demand. There has been a steep increase in what kind of price tag they are commanding. $1000 might have bought you one two years ago. I have seen them changing hands recently, complete with accessories in the transit chest in the $2500 ballpark.
A very limited number in civilian hands. Only getting harder to find as there will be no more released, the ones currently in service are destined for being made into cadet drill rifles or off to the chop saw.
There are also some parts rifles doing the circuit put together on scrubbed receivers. Elwood Epps was selling stripped receivers some time ago at $50 a piece. They appeared to be unissued.
The clones can usually be detected by the 303 barrel fitted with a barrel liner, whereas an original has a one piece purpose made 22RF barrel.