"How much" is asking for a quantity. "How" by itself is asking for a means or method.

Example 1:


  How much will you pay for me?
  
  I'd pay up to $20.


Example 2:


  How will you pay for me?
  
  I'll pay with a credit card.


By the way, both sentences sound, at least taken out of context, like the speaker is asking the person about buying him or her, like you would buy a slave or a prostitute. Perhaps the intent is that they are asking about buying something on behalf of him or her?

"you will" vs "will you"
I am trying to install a front wheel in a bike - the axle of the wheel is threaded, but I have trouble finding out what size thread it is, and what nut can go on this. The size of the thread on the axle is the same as of a 8 mm screw, but a standard M8 nut (with 13 mm hex) does not fit on it. Do bikes have some special kind of nut there?

If I look at the thread, and at a standard M8 screw, the thread on the bike axle is a bit more dense then on the screw, but I am not aware of existence of two kinds of M8 nuts, so far every M8 nut did fit every M8 screw.
