Translation:He is afraid of having to pay too much.
Behöva can mean need, but also can mean need to or have to. I am just a student here but my impression is that there's a bit of a scale that goes something like: behöva = have to -- måste = be compelled to -- tvingas = be forced to. In the context of this sentence, the weakest form fits best.
The second "för" in this case is "too" (as in something excesive), so "för mycket" is "too much". What the sentence means is that he is afraid of having to pay too much money (for whichever good or service he was acquiring); not that he is afraid of having to pay for much (meaning for many goods or services).