Well given the shape the one I have is in, and the person I got it off of cared to use one of those plastic game holder box things (I don't have others) it's in very good shape probably an 8-9+ range I can only wonder what someone would think if I cared to (and I don't) part with it as that's nuts. Gameboy games alone are reasonable, you bundle them up with all the original bits it can get very crazy.

*tosses hat into the ring*

I recently picked up a Red Complete in Box with all of the paperwork. The box is decent to good condition along with the paperwork. The cart and label are in great condition, and look just like new. I already own red cartridge, and because of my purchase, I now have 2 of them. The difference is that the one I owned prior to this purchase, was my birthday gift when I turned 7... and I held onto it for all of these years because that game took me to a whole new amazing world that really ramped up my love for rpg's and gaming in general. I used and abused that game. And as such, the label was tearing off. The box and paperwork/manual are long gone... 
Now on to the purchase: I paid about 70$ for it. I normally see a comparable go for 100+. I was able to get it for 70$ because I waited for about a year, and slowly hunted on Canadian eBay. I knew exactly what I was looking for: the Canadian dollar is currently .74c to 1USD$. I waited a year to find a Canadian who had made the mistake of listing a BIN at roughly the USD$ value of the game CIB...and would be paid in Canadian Dollars. (This arbitrage gives me a 25% discount on the game). The person should have accounted for the 25% differential between the Canadian dollar and the US dollar. 99% of people do this... but I knew if I waited long enough, I'd find the person that slipped up.

I bought the game CIB so that I could feel EXACTLY how I did decades ago on that night of my 7th birthday... and you know what? It didn't disappoint. It felt great holding that game again, and remembering exactly how it felt to read through the book sized manual that came with it, overly excited to pop the cart into the gameboy and start playing.

The overall point I'm driving at here:
There is a difference between collecting and investing. And while the two actions can coexist, there is an art to doing it the right way. In my example, I wanted the game so that I could literally time warp myself back to those feelings of excitement the night of my 7th birthday. But I executed the purchase in a way that may or may not allow me to at least recoup what I paid for it, and maybe even a bit more, should I ever decide to sell one day. I work 2 jobs, one on wall st.. and I see people mixing up the definition of what it means to truly invest in something all the time... and my answer is usually the same every time.
Patience pays.

My 2 cents  

Ever since prices started getting crazy like what eight years back now I've had to re-assess everything I pick up anymore much like what you said, both for the memories and in a way like an investment and I do hate that. Anything I grab now I make sure the price is something where if I dislike it, I don't lose, prefer to profit, but equally acceptable to get out even after any fees and charges around putting it back out in someone else's hands.