I remember when Chechen and YNAO were in 30-50 euros range and I just laughed and left it be. I was sure it was some kind monopoly going on, like one or two resellers getting exclusive access and bought majority of the circulation for sale. Since they're quite low face valued, I assume it would be extremely profitable and one can easily buy thousands of it, even whole mintage.
I was sure prices will go down after a few months. That did not happen, they only have risen. Now, at shown prices, a seller would pay off entire price of buying the mintage by selling only 50 coins during the years. Imagine that!
So, somebody is extremely stubborn and persistent. Raising number of Russian collectors can't explain the trend, even the euro coins, which have incomparably larger "mania" can't get near to these prices for similar mintages. Also if I'm right, big game collectors in Russia are generally interested in tsarist period. Increasing number of bimetallic collectors can explain why all the other coins disappeared from circulation.
In that case, prices could go down in 10-15 years, but not much, maximally to the level I mentioned at beginning of the post, plus the inflation of course, because the source will still be stubborn, it paid out its investment long time ago but there is no more interest in this coin. There would never be 100000 people in the world willing to pay 100, 200 euros for a new coin with such a mintage.
There is a whole trend of overpricing coins on ebay and it surely does affect both 1$ auctions, regular price settings, other auction sites and traditional auction prices. It's a whole new problem also seen here.
The other option is, like ciscoins pointed out that not all have been minted or put in circulation. If they're held in some bank treasury a considerably few will be able to escape to the market.