FSA USA lists these parts at $33. They are out of stock, but I would drop them an email to see if they can get you one sooner—super friendly folks. Just buy it from them.
I've done some work for the Tarmac SL7 and SL8, and it's tough to go lower in terms of stack height because of how the hoses need to run. Also, it's tough to go lower on price unless you can do relatively large production runs. I don't pay myself for the time I spend designing the parts I make, w/100% of the profits still going back into new product development, and that kind of pricing is something I can only offer on my higher volume products for the PA12GB stuff. As far as I know, the other sources for 3D printed headset covers are similar in price, too.
If you were to use standard PA12 and find the cheapest SLS supplier, you could cut the price down to like $20 if you were doing runs of a dozen or so parts at a time. I wouldn't ride that as a permanent solution, though.