Did I get screwed buying my black pipe

As a plumber I really try to shop at regular plumbing supply houses instead of the big boxes. #1 I get good service because I'm a regular there #2 They stock plumbing supplies only! no blenders, blinds, carpet, etc. #3 they almost never have to order what I want, and if they do, I can have it overnight-ed. #4 If the small supply houses don,t survive we won,t have a choice of where we shop. #5 I can buy 1 of something or 5 of something I don,t have to buy two bags to get 4 of something. #6 The counter people know plumbing parts. #7 they don,t say its in aisle 10 Enough said! My supply house charged me $51.60 for 21' of 1 1/4 black pipe,$3.11 for a 90`$ 2.82 for a coupling. A word of advice do not use the coupling that came on the pipe that is for protecting the threads ( they may have a running thread!) you mite be a wee bit upset when you fill the system and it leaks. The bitterness of poor quality lives on long after the sweetness of price.!

I found the same type of pricing the plumbing supply was a little higher on some of the items both black iron and copper but the quality of the fitting was much better on both as well. I ended up using some fittings from the big box stores as I found additional parts were needed but some of them were so poorly made they didn't hardly fit together and I ended throwing a few pieces away so in the end the price was a little closer to the same and in one case we had to drain the system twice to fix a leak and ended up replacing the fitting to solve the problem so those type things also need to be factored in. The counter guys also were helpfull in designing and finding the right black iron parts to minimize connections and space and we ended up using quite a few fittings that the box stores don't even carry and I would have spent more buying extra parts to make the same setup.
In your case I would just lean on the supply house guys and see what they can offer .... a few free parts , supplies or tools .... borrow tools ..... free design help... few extra points of discount ..... free trinkets hats shirt gloves you never know until you ask.

I agree 100% get your fittings from a plumbing supplier they are a better quality (hopefully not China made if they are walk out), but my local supplier only had precut and threaded pipe for sale no custom sizes, so all my pipe is from HD and all fittings are from the plumbing supplier keep in mind to use some tees where temp gauges are needed and small air seperators..Dave