Well, if you want to do it where the #bot spawn command is processed in bot.cpp, you could add this around line 12424:
Code:
if(!c->HasMoney(c->GetLevel() * 1000))
{
c->Message(13, "You don't have enough money to spawn a bot.");
return;
}
c->TakeMoneyFromPP(c->GetLevel() * 1000, true);
That would go just before the existing line:
Code:
Bot* TempBot = LoadBot(botId, &TempErrorMessage);
At that point, the variable 'c' is a pointer to the client that is trying to spawn the bot.
Note that the HasMoney/TakeMoneyFromPP methods take copper as an argument, so 1000 is 1 platinum.