They can be as little as you want to make it.  
Something like $1 cash discount if you pay by 
Money Order or Check.  

So if you're standard shipping fee is $5, charge 
$6 in your description.  Then, if they pay by 
PayPal or Billpoint, the fee is covered.  And if 
they pay by check or money order, they pay $5 
shipping, what you normally charge anyhow.  

And it's not just eBay pushing Billpoint.  
Passing on your surcharge for accepting credit 
cards IS illegal.  Adding $1 handling to your 
shipping charge, building it into your opening 
bid, or charging a cash discount is not.  

BTW, PayDirect is excellent.  I wish more people 
would give it a chance.