At 280$ for the package, I'd say it's a fair price assuming it is in good condition as described.
For me, used gear need to be at least 60-70% off of regular price to be worth it.
New 390 Boss: ~ 300$
New NS SL: ~520
slyder: don't forget he's in Canada. Prices are often higher right off the bat and we rarely see clearance like you see in the U.S. And shipping price from a US dealer often kills the deal.