Ten or fifteen years ago, looking to price and buy a gun was done mostly locally, or by phone, word of mouth, print media, gun shows and a very small proportion by various internet channels. The total number of potential buyers was fewer for any given sale and thus less pressure up on the prices.
Now, with everyone having quick and easy access to the internet, anyone selling a gun knows they can price it not just for their locals reading the paper or seeing it at the shooting range or on consignment, but for anyone in the country with a license. With so many more potential buyers, the prices and rise fast and STILL people will buy, giving incentive for sellers to raise the prices even more.
Adjust for inflation and increased value due to fewer good examples available and the prices of milsurp stuff today is still artificially high. You can blame the internet for this. Anyone noticed the same thing in second hand/consignment stores or used book stores? Those little gems that nobody knows the true price of are very very rare to find now. Every little shop owner has eBay handy to check and they ask the same or higher than others are selling for. Same thing is happening with milsurp. I'm sure someone could do a research paper on the weird economics caused by the internet on niche markets.