For me, Retro gaming has always been the budget option. And outside of a few rare example where the value of the game was about to sky rocket (see Pokemon XD), I usually wait for the price to make sense to me.

For me that price is between $5 and $30 depending on the game, system, and how good that game is.

When I see Cars for the PS2 for $3.99 at a thrift store, I'm not going to say no. But $300 for the SNES version of Chrono Trigger, and the sellers, and the ~~idiots~~ influencers that buy from them, are out to lunch.

For these games with hyper inflated price points like Chrono Trigger, or Conkers Bad Furday, what I usually look at is re-releases or ROM collections. For a game like Conkers, you can literally buy an Xbox One and Rare Replay for less than what the cart is selling for. If you get lucky you might even get OEM controllers.

With most retro games outside of license titles getting remakes, and re-releases you should look at remakes before the original. You can probably build a sizable retro game library from the various ROM collections on steam alone. But if you want to play on the original hardware, I do advocate for Piracy of Hyper Inflated games like Pokemon Emerald. Especially since those scalped prices are not going back to the developers who made it, and Nintendo appears to have no desire to ever re-release them. So in my books they are as good as abandon ware, and one foot in the door to the public domain.