Well because if someone were inclined to buy an item now, they will buy the lowest priced one if they are all the same item and in comparable condition. That is why you check the current listings and then undercut them. On the face if you listed a keith courage for 10k, this does not change the market...unless it sells. Highly unlikely but if someone really did complete a transaction for keith courage for 10k it would effect the market. To what degree, I couldn't say.
Regardless of how over priced everyone on here thinks the listings are, that doesn't mean people won't pay it. That's kind of why the market is shifting. It has every bit to do with demand as it does supply. In fact, I'd blame the ones buying the inflated prices more so than the people listing high prices. If one is patient they can find a fair price for these games. Necromancer's quoted prices prove that. Let's face facts though. No one younger than the people who played these systems in their youth has patience to wait to save $3 or $5 or $10 on a retro game especially when they are used to brand new current gen. games costing $60 a pop. Does it cause the market to go up? Absolutely it does. We in the community are forced to bend to the prices set by outsiders and that's frustrating. This really is just business and economics 101 though. Supply is finite on these games. They aren't making any more of them. The only thing causing this market to fluctuate is demand. Every new person starting out collecting TG16 gear is why this is happening. Until that slows or decreases, the sky is the limits on the value these games will have. Short of all of us dieing out or a re-release of these games or a crash in the US dollar, I really would expect the prices we see online to just continue to climb and probably at an accelerating rate.
Take Magical Chase for instance. I came across a forum (not this one) thread for one for sale for $300 about 10 years old. For 2010 I found a few that sold for $800-$900 and now pretty consistently they are going for around $2000. That's not a fluke. That's a trend. On that particular game we are currently looking at a 13.75% increase in value yearly. Next year it'll be going in the neighborhood of $2275 by my estimation, if not more. If I had disposable wealth, I'd honestly be buying up magical chase copies like mad. Can anyone name me an investment right now with an interest rate of 13.75%+/yearly and the security of knowing this market isn't going to change for the worse any time soon? Think about that! The values of these games is stronger than the US dollar right now.
I'm just as unhappy as anyone here is about it, but I chose to try to inform myself about how and why the market is doing what it is doing. I'm still no expert, but just complaining about it is like a rocking chair. It's something to do, but it doesn't get you anywhere.
Before anyone accuses me of being a gouger, I'd like to just state, I've never sold or even traded away a Turbo game. In fact, the extras I have are going to be given away. I enjoyed Nullity's picture competition and I'm trying to come up with a similar kind of competition here which will have my extras as prizes.
