Welcome to WaGuns, Peter!
Some dealers will charge per gun, some will provide you a discount on multiple items. Handguns tend to be more expensive than long guns because of the additional paperwork.
We have a few dealers listed in this thread:
viewtopic.php?f=51&t=63268Also remember that the FFL will charge you WA use tax (aka sales tax) on any guns that are being shipped from another FFL. If they're being shipped from an individual, they won't charge you use tax -- you are responsible for that yourself.