Apparently, the ESRB is adding to the high cost of PSP Minis, especially since mandatory ESRB ratings for each can cost developers $2500 green ones.
"You have to invest some money into dev kits and into getting ratings for your game," Fieldrunners developer Sergei Gourski told Gamasutra. "The costs of ratings such us ESRB is significantly more then we had realized".
Titles developed for iPhone can forgo dealing with the ESRB, but it's not like the agency's not trying to get that to happen.
For now though, Apple is the sole ratings system for the iPhone and while that may sound like a boon to developers, Sony takes three to five days for approval, while Apple approvals can take up to six weeks.
More through Joystiq.