I think he charged me $155.00 for my last set of 704,, 85.deg Spring-Airs. Comes with everything needed for install. Air tank, valves, Ts, hoses, connectors and air line attachments. And a manual.
As Edwin mentioned,,, the 3/16" wire inserts are standard with the units although you can get the 3/8" inserts and use an adaptor. I kinda like the wire inserts for these CMP birds. Bending the wire slightly to get a good fit into the wheel wells is easier than shimming the heck outta the retract unit. Plus it's better to bend the wire after a hard landing than a strut.
There are better custom built struts out there for sure. But I've never found anything better in a retract unit than Spring-Air. At least for these lower priced CMP kites.
Gearing a $3000.00 + warbird is a differant story. Although he makes units for mighty big warbirds as well.