Current Party GP Checking and High Prices

A custom command like that could be created I'm sure, but no there is not a 1 byte command at the ready, the C0 check is the only way to check if the party has enough GP, by checking the bit designed for just that. Still you would need to have a subcommand for if the party does not have enough, which could also be in that custom code, but it's nice to have different addresses to go sometimes if not enough GP.