IMO, one of the major limiting factors for new milsurp collectors is the availability of cheap milsurp firearms and ammo. Most folks don't start right off as collectors, rather they start as shooters or hobbyists.
When prices of guns and the ammo to fire in them goes up, up, up or the supply disappears, the cheap "gateway" into the collecting world is eliminated.
In Canadaright now, I believe the greatest milsurp interest is in SKSs, SVTs, and Mosin Nagants, precisely because the guns and ammo are commonly available and for reasonable prices.