This sounds about right. As an engineering I can say you really shouldn't call us for anything you don't really need us for.
for your money you got: A bunch of calculations done to the building code (not just the contractor using the proscriptive table) which saved you some amount of material. It probably didn't save labor because engineers tend to be good at optimizing material and not labor. You also got the all mighty stamped report, which means this guy has insurance and liability if his design doesn't work. But it also got you a stamped report that if a local inspector wants to hassle you, you can hide behind engineering.
I also gotta say at least on the industrial side, if I do the work and give you a solution, people balk at a couple grand fee. If I do the work and give you a fancy report, a 10k invoice flies through no problem. Its even better if you can attach a couple full sized drawings, those always intimidate and justify billings.
And as Bucks suggests, this kind of stuff can always be done lump-sum.