I sold some expensive items and then check on the ITEMS AVAILABLE and this what it said about the money
I think it's because u passed the max mesos (which is 2^31 - max positive integer representation of int32) If u get more than that then u get 1 on the 32nd bit which tells the system if it's + or -. I think a fix for that would be going into the client and change the type for all int to some long or whatever... not sure if the devs can do it. If you really care about this number I'm pretty sure that they can make it that stores cannot sell for more than 2^31 mesos at a time (but then it will mean that after u sold the king cent u won't sell anything till you reopen. I'm pretty sure u don't want that)