It might not look like a Maslow yet…but it will. The top header is a perfect 12’. Now for a few cuts here and there and some bolts and a possible tack weld or two and it should start to come together into a frame that won’t flex or warp 
So far cost = 0 ….unless you count neighbors kids being upset that their swing set is missing.
Haha, great reuse of martials. I’m excited to see it finished.
Now you do realize that you have to leave all the sawdust on the floor below it for safety reasons. 
I plan to make plenty of sawdust !
good luck, I hate working with round tube/pipe. buy a piece of angle, it will let you keep a straight line along the side of the tube. Nothing worse than rotational errors.
If they are too upset, just create a new wooden swing set with your maslow 
Oh yea… there will be some angle in there. That’s where the cost will be encountered given the steel costs.
