if you are handy and have some space (read: not fitting your skimmer in your stand/underneath your tank)...then it is basically impossible to beat a well designed and well built counter current skimmer.
if you dont mind the ugly factor...you could make an absolute killer 8" skimmer that is 6' tall, along with the feed pump, airstones etc for well under $500. what is ugly?
no, not this:
but it sure is up there in the top three.
ugly would be the whole thing made of opaque pvc:
http://www.hawkfish.org/snailman/diy8inskimmer.htm
i modified the design a little to be a little better (a little more $$$ but aesthetically more pleasing).
i have found CLEAR PVC in 8" diameter etc...with the end price being somewhere near $1000 for a complete 10' skimmer.
i may be stepping on a whole lotta toes...but i seriously doubt that any 'consumer' (please dont link the $25k rk2 skimmer to my response) skimmer would come close to this skimmer. i was in the middle of planning it until a 390g acylic tank fell into my lap and has since distracted my energies!
what to do with a 10' high 8" diameter skimmer? power it with an alita 60 airpump (an alita 80 would kick even better) along with a 6 to 8 airstone skimmer manifold. with the availability of uniseals now...it is so much easier to drill and attach pipes to cylinders now.
just throwing out options...
sometimes the 'bought' stuff isnt always the best! again, my opinion only...