Ost relief inf is probably the worst ability there is for Ost. Even worse than Railway arty. You spend 90 munis and you need to drop 5 models most likely 5 gren models = 150mp to get an Ostruppen squad (worth 200mp). U save 50mp at a cost of 90munis and the risk of losing an entire squad or wasting 90munis cuz u didn't get 5 models to drop in the span of 40secs.
This ability was clearly overnerfed. DO NOT USE THIS WORTHLESS ABILITY AT ALL.
It's not literally "spent 90 muni and 150MP each to get 200MP back" though, it requires you to lose the models probably through fighting the enemy back (unless you know they got a mine field you can suicide through I guess...), which has its inherent benefit of "trying to not lose the game", so I don't think it's fair to simply consider regard the resource expenditure as that.