We treat them like any other edits however unlike edited films we know there wont be any amendments so we only need to charge for the initial edit. Normally we can put a B-roll together in a 2-4 hours so we price accordingly. We've got it down to a process now where one of us will actually edit most of the b-roll while we are on the actual shoot. It's a great way to check the shots but also saves a lot of time when we get back. This also means we can deliver very quickly after a shoot which clients love.
The Sony FX3 has been my workhorse for b-roll over the last year or two. That said the Blackmagic 6K Pro is great as well. Nearly all cameras from the Pocket 4K up can do a great job, personally I'd say 4K 60p is a minimum but good low light, like the FX3 is a huge bonus.
