Orrimarko,
CIB games, TG-16 is at the point now, where the prices are really stupid. They MAY settle down later, they may not. It depends if people are still keen on them as time passes.
10 years ago, there were some good deals. Telegames/Direct4games cleared out their stock of new games. I picked up Darkwing Duck through them. yeah, it sucked, but, I didn't have it, and I probably paid no more than $15USD shipped for it, from the UK..
TZD is gone. Red Frog bought the last of their stock, had some stuff for OK prices, then they had some sort of legal thing, which made them shut down. I'm not sure where that stock went, or if it is tied up in some legal limbo?
It used to be, about 10 years ago, the craziest price out there, was when is aw a CIB Magical Chase sell for $500. A year or 2 prior to that, (2002?) I think it was going for about $200-$300.
Now, TG-16 is "cool" with more people. Supply and demand. I said it here before, if I were JUST getting into TG-16, I'd get a flash cart. I have one now, for PCE stuff I never bothered importing or buying from ebay.
During the first 10 years after a system's death, that's when you can get OK prices, especially the first 5 years after it's gone. I've noticed, after 10 years, prices tend to go up. Re-releases help, such as the Virtual Console TG-16 stuff, then again, they can also make more aware of games, systems, etc, and that can increase demand. blah blah blah.
I noticed, after the virtual console stuff on the Wii, TG-16 prices went up quickly. It's stayed that way.
To own all the games, and such, for TG-16, you're not going to find it cheap. Ebay took care of that. Goodwill now tends to check prices for things before putting them in their stores. Heck, even with books, not many carry them anymore, and instead sell them in bulk to book resellers who buy the books, by weight, so they can resell them.
I miss the days, when I could find all sorts of stuff at goodwill stores, yard sales, etc. I purchased the Atari 2600 game, "Quadrun", years ago, at a parking lot neighborhood flea market, for a $1 or something, back in the late 90s. I didn't even know the game was rare, at the time. I don't expect to encounter that again.
Deals, through people here, when you're new, you'll have a hard time with that. It's been witnessed before, people buying stuff, getting good deals, then reselling stuff on ebay. Also, some people go for it, get really into the system, then decide, they want to dump it, due to lack of interest, bills to pay, etc, and they tend to go to ebay. Don't be bothered much, that people are a bit guarded about things.
Not much more to say, that hasn't already been said....