How about this:
The cost to propose a delegate is 1 day of delegate pay.
Thus, to propose a 100% pay delegate, its around 5000 BTS.
For a 10% pay delegate, its only 500 BTS. (I think we need to allow these partial pay delegates to be proposed at a reasonable cost. After all, in the future when BTS is worth a lot more, I think most delegates wont actually be max pay delegates, because max pay will be a TON).