Goals are arguably the hardest currency in football. That's why strikers cost so much. I agree that Bale hasn't looked "all that" for much of the season, but scoring 11 PL goals from 20 matches, especially given that he's had limited minutes, is a pretty good return. That's a striker's scoring rate.
We'd be paying £100k/wk to get pretty much any established striker. If I was offered an experienced backup striker who'd score a goal every other game, for a £5m fee and £100k/wk, I'd be biting his agent's arm off. That's equivalent to what we'd be paying for a year of Bale's services.