I have seen no news about a stop issued to importation of Mosin Nagants.
A rise in prices is not evidence of a stop to importation.
In 2004 I paid $129 for a CZ 52 pistol (plus holster, two magazines, cleaning rod, lanyard) and such deals were common. Today they are harder to find and the price is higher. Not because of a stop on importation, but because there were only 200,000 made 1952-1954 and most apparently have been surplused out.
Mosin Nagants were made in the millions and with the end of the Cold War were released from military reserve for collectors, hunters and military match shooters. I suspect batches will be released from time to time, but the reserves are less than they were decades ago.