This is not really true I don't believe earthbound is uncommon at the very least rare in the lower end if not a bit higher.
Sought after games that sell fast for a nice value will turn up on the market allot faster, Heck even allot of collectors with buyers remorse etc will sell it again, or when money needs arrive it will be one of the first thing for sale reseller or collector not every buyer can keep it for long.
Same can be said for symphony of the night ps1 european version that is wich I've only seen 8 of over the years only 1 collectors editions in non collectors hand potential for cheap deals yet collectors always sell it when they are in a need of money, same can be said for suikoden 1 & 2 etc wich are less rare than that game but still very hard to find. with 50 + value items especially when sought after people will feel the need to sell them they rather have the cash than the game. Many copies of these expensive games have been switching hands many times so naturally you will see many copies on ebay etc. with the less valuable titles switching hands and going up on the market again is allot less common unless someboy quits collecting.
I've seen people buy lots selling titles as suikoden the rare stuff because it has nice value while keeping the mediocre titles since it's cheap no matter how cheap the set was. For allot of people they rather have the money than the game it seems. Especially anything goes collectors that rather collect quanitity over quality will sell those titles in a heart beat even if they never come across one again, they just sell it after playing it some times if not immidiately. It can be emulated and they can spend it on more games to each their own I'd say
Than again for allot of people that 50 - 100 $ + is allot they can do other stuff with it, so collector or not allot of people can't justify keeping a game that has that much value. Gameplay wise It's a bad thing but I can somewhat imagine why they do so. Tons of people who think that way with retro games unless It's a current gen game or current gen collectors edition than it's okay
Panzer dragoon saga very rare yet always on ebay since again you'll gain nice amounts of money. european version only has 10 to 15K copies but valuable items that sell fast are always nice to put up for sale.
Extremely rare probably not but probably rare in the low end compared to the rest if were talking about earthbound. If it was only uncommon the value would be far less and cib it would not sell for near 1K. if it were just uncommon a lose cart would only be around 70 ish if not far less I'd say including the hype it has today. Many snes games are hyped but I'm not seeing your Dk countries or super mario or contra carts sell for 50 100 etc hype can also get a game so far as far as value goes. If it were just uncommon I Can't even see a cib one go for over 200 to be fair even with the hype.
If the value of earthbound wass less, way less copies would be for sale I'm pretty sure of that. Furthermore look at chrono trigger is that game just uncommon I'm pretty sure it is more rare than that? Goes for way less than earthbound, if eartbound was just lighty uncommon the price doesn't make to much sense it would be way less valuable than chrono trigger maybe slighty higher than super contra etc.
The demand and value is what keeps even collectors selling them games for fast cash and resellers buying them up for a profit wich includes collectors who need fast cash thus ending up on ebay.
Chrono trigger sold almost 300K copies in the USA earthbound 140K to 150K so I guess in those numbers it is rare for the demand it has and that other titles had way larger sales.
Than again if the ds ever gets such a high demand as the snes chrono trigger on ds it might be priceless with less sales so in that aspect I can see where your getting at.
Still though many carts are probably broken and as far as cib goes I'm pretty sure a pretty low % has survived maybe less than 10% if I might guess.
Than again if say retrogaming becomes less popular people get out of the hobby and only 50K people are left It's just an uncommon game with less demand than the prices might be fun with those amount we might see those low prices
. but if say a few million people are into retro game collecting than prices will stay high I guess.
the amounts might seem like allot but it really depends how many people are into retro game collecting today.