Do reserve keepers get paid over the ordinary as compensation for the fact that they'll rarely get game time? I'd say that's a price worth paying. I know they are supposedly meant to fight for the no. 1 (or no. 23) jersey, but the reality is, you're there for the few moments of cover required. I can't work out why most other PL teams manage to attract decent level back-up keepers, but any time we think of one, there is always a caveat in the way of us seemingly attracting them.
I would think the promise of a few months' head start to establish yourself as first choice with us next season would do most keepers nicely. Last two seasons have shown me how important a reserve keeper of the right age, agility, temperament, experience etc. is - I reckon we've dropped 5-6 points as a direct result of not having the right level of backup. Pure guesswork of course, but even the positive psychological effect on the opposition is enough to change the result in their favour, not to mention any negative psychological effect on our defence.