Question about repair costs

Hello,

I play on android and i'm wondering if there is any difference in cost when repairing with Repair Drones, Repair Modules, or System Repair?

I usually find a repair module and my strategy has been to leave the module in storage until after a battle and then equip it to repair. I notice that this also uses my scrap. I experimented with repair drones as well. So is there any cost difference in any of the different repair options?

So far I know that station repair is free but i can't tell if the 3 options that cost scrap are all equal. Also does upgrading the modules have have effect on their cost? IE would a fully upgraded repair module cost less scrap to fully repair your ship than one that hasn't been upgraded?

Thanks!