The cost basis is recorded for each item.  Keep track of the total cost basis like you do for the total value and total game count.  Keep this value private though like other cost basis info.

I have too many games in my collection to keep track of mentally. I'd like to instantly see which games in a lot I already have so I can calculate weather or not it's worth buying a lot to get bulk games I need.

The Epoch Cassette Vision is the first Japanese exclusive video game console to feature interchangeable game cartridges. Of thirteen known games, only eleven were released.

I'm trying to collect the entire PS3 catalog and having the option to only see games I do not have in my collection would greatly increase the efficiency of searching.

Please add prices for Japanese Mega Drive games!! There are a lot of exclusives that didn't even get an European release...

Also, thanks for already adding Famicom and Super Famicom!!

Adding The cartridges for the Texas Instruments TI-99/4A would be nifty .Mattels Hyperscan would be a shortlist  but might be nice as well. 

The Commodore Amiga CD32 is a CD based videogame console of the 90s. 

Please add support for it.

Thanks!

Please add polish language and currency-PLN. Thank you.