Hello Doug,
As you might have noticed, my active colleting area is Russian and Japanese coins.
Russian gold coins actually do have quite a fair bit of sad, if not dark history behind them. Taking the example of the last Tsar gold coin - Nicholai II. His gold coins was minted till 1911, and that was when the Russian economy started to crash. Soon gold was too precious to be wasted on coinage, and as the debts grew, gold coins were melted down and were made for foreign payments and war fiances. Knowing this too well, probably some mint officers ordered a hoard of gold Tsar coins to Sweden The Tsar was overthrown in 1917 and that was when Russia nearly killed the existance of precious metals in coins.
When the Bolsheviks took over the country and became a RSFSR regime, almost all gold coins that could be found were melted down and a new bullion gold coin was minted only in 1923, which was then known as the chervonets.
An example is here:

The following year, RSFSR was then known as what we know as the USSR. The regime became a total totalitarian regime and people had to give up whatever precious metals they had. It wasn't much later than Soviet silver were gradually removed from the coinage and in 1930, there were no more precious metals in Soviet coinages. Whatever precious metals were kept were either melted down as bullion forms and sold overseas or kept in the vaults of the Soviet mints for future uses.
It wasn't until the Soviet Olympics that the Soviet mints could use their chances to mint their coins in various precious metals. In 1977, gold chervonets restrikes were once again revived and the Soviet mints started to mint at insane numbers. Once again, stashed gold Tsar coins were rumored to be melted down for such coinages.They as well minted insane number of commemorative coins for the Soviet commemorative coins, such as gold, platinum and silver. The problem was - the Soviet mints minted WAY too much coins - we are talking probably over 60,000 of troy oz of gold coins if we included the chervonetz and gold olympics. Metal prices went to insane prices in the 1980 and again, the once minted Olympics coins were sold back and forth, making the whole massive mintage in precious metals meaningless. The Chervonetz were then officially cancelled in 1982.
It was only a few years later in 1988 that the Soviet mints decided to mint commemorative coins in strict mintage figures. Often, mintage figures are quite low, averaging from 1500 for some odd coins to at most 40,000 for some silver coins. I guess they have learned their lesson of the shock result of the overproduction mint tragedy.
This alone is not the end of the story. Remember how the Soviet Union dismantled? This caused enough headaches for the Mints as they were basically left alone with almost zero support from the Government. Perhaps this was a bad idea since this meant that the Mints are now free to mint whatever they would like to as well as not limited to the metal specifications. As a result, Russian Mints started to mint ridicious coins which even includes 1kilo gold coin and 3 kilo silver coin for their record! You may check their current catalogue minted since 1992 here:
http://www.cbr.ru/eng/bank-notes_coins/Bas...emorable_coins/Nowadays, UNC Tsar Nicholai II gold coins out in the current markets probably come from the vaults of the Swedish banks. I seriously doubt if the Russian vaults still have much left. Now finally going back to your question of why Russian gold coins are expensive, one simple reason may be because no one has an idea of how much is left! There might be records that millions of gold coins were minted, but no one knows what and how much other gold coins were scrificed for the sake of newly minted gold coins.