We don't "have to" pay too much, we simply want the best available. We could easily replace Milner with a hard working squad player without any dificulty or expense, but we want the best. Whether we did that this yer or two years ago it still would have cost a fortune. (and I don't really see many english players around a couple of years ago worth paying a fortune for)
The homegrown issue is completely blown out of all proportion, the HG players we're losing didn't play that many minutes any way, they could just as easily be replaced by a foreign player if we got rid of some of the dead weight in the foreign quota (looking at you Jovetic, and you Willy). Buying a HG player or two will just make things easier, they aren't essential in any way, shape or form. Milner is the only HG player who we've lost who actually requires replacing and there are tons of ways of doing that without even needing any more HG players.