Considering that on average it takes like, 3750 cores to get a 5* tank (1% chance and one at 100 loyalty points), 1k cores for one is a steal. Be aware that getting an Elite Satan + Elite Waffles for just a few purchases of bags + playtime is probably an even bigger steal, though, so you might want to make sure you have some spare cores to buy ghost and wing bags if you need them. ...maybe.

I've produced over 1500 (probably 2,000 by now) tanks from the factory and only got one five-star out of all that, by the way.