He isn't much of a friend if he intemtionally shafts you. So like I said offer him $400. If the system is running, it's worth that. G3258 system is worth nearly $400 w/o dedicated Graphics. And doubtful that clock speed messed anything up. It might have limited further adventures to 5. But it could also be like when someone rattles off numbers off the top of their head during conversation... i.e. "never happened".
Telling whoppers is what guys do. And they aren't specific to Fishing stories. Not lies, just the fish grows and the fight more difficult with subsequent retellings.