Go here:
http://www.apple.com/legal/itunes/us/terms.html
do a search for this phrase: "MAC APP STORE PRODUCT USAGE RULES"
Namely, you would need just as many App Store accounts as there are seats (if 8 workstations then 8). If 8 folks shared 5 workstations you'd only need 5. However, if there are employees who have it installed on Mac Pro and their MBP then ony need to by one for that employee (the presumption is that only one of those are used at a time).
the "iTunes covers 5 computers" thing is only valid for personal/home usage, not commerce. For personal usage mac App store is any many macs as you "personally control". If own 10 then it is 10. Obviously, they are not gong to let a business follow that rule since have resources and/or need for many. The limitation varies by who is buying what in which store. It isn't uniform.
At some point Apple is going to have to fix the "stores" so that they can due volume/bulk licensing. So far it is pretty ad hoc. If they plan to fix that soon it would be better to roll that out before Lion ships. However, given Apple's SNAFU release track record it would not be surprising to see them roll it out in the middle of the Lion update maelstrom.
Well, there was a volume license for the last Final Cut Studio (what we have) and it saved us some money. We don't really need volume licensing for some of the other apps in the FCS bundle (really don't need more then one copy of DVD SP, and Soundtrack). While FCPX is cheaper as a single app, it might wind up being more expensive now to buy that, plus motion X when it comes out, plus a copy of Soundtrack, etc etc.
Either way, when dealing with many many seats a volume install makes life a lot easier for both seller and client. Thank god I don't work at a huge post house, what a pain. (Although, they probably already have a plan in place for this)