Yes, retro game prices have got increasingly stupid in the last few years as you've now got investors muscling in to the market to try and turn a profit which is pricing normal customers out entirely. Hence why bootleg carts from China have gone from barely being a thing to generally the only affordable option, and why most people are just buying flashcarts.
In particular the American market is the worst hit, even run of the mill games have seen massive price spikes. A year ago I wanted to import a Genesis copy of Scooby Doo Mystery but didn't because no decent copies came up that the seller would ship to the UK, there were no bootlegs at all as it was still a relatively cheap game. Now the game is most than double price it originally was and the market is flooded with bootlegs. The PAL market has also got quite costly, however prices rise at a slower pace and over a longer period of time.
The Japanese market is a bit more hit and miss, most well known rare and expensive games haven't really gone up much, however a lot of stuff occupying the mid-range has doubled, and a few titles that used to be on the low end of expensive are now basically unobtainable. For example with the Mega Drive you've got Snow Bros, one of the rarest JP releases, which is about the same price as it was 10 years ago. Twinkle Tale always was one of the most expensive and has doubled, Trouble Shooter has basically jumped 5x, Sailor Moon went from being pretty cheap to triple digits.