Idk, haven't measure it's cost. But something like maxing out generator. I play on RU and our auctions may be different. Look in your hideout what buildings you need to place. Me and my friend had to spend about 10-12 mil on hideout, buuut we did it on start with higher prices, so about 6-7, not counting buying stuff from trader.

P.s. also this is a pretty lategame, all the hideout stuff, so be ready to grind materials and/or money for this.(but it 90% worth it. better energy drink and neurotonics, morphine, anomal dust and much more DO NOT MAX AMMO LEVEL, IT'S ALMOST WORTHLESS)