The starter contactor for a 12 volt airplane is a repurposed automobile contactor. That keeps the price down, sort of. The 28- volt contactor doesn't come from any car that I know of. Its coil has to be of finer wire, many more turns of it, to limit the current. Big trucks use 24 volt systems, but their contactors are huge, to handle the much larger amperages their starters draw.
Besides that, how many 24-volt contactors would one sell in a year? How many of you owners of any airplane ever bought a new contactor? It would be a tiny volume, which is one of the reasons they're expensive.
You need to build stuff that costs nosebleed prices from the OEM and that isn't available anywhere else. McFarlane has done a good job of doing that, and Cessna even buys some of their parts from McFarlane now.
McFarlane makes the stabilizer trim jackscrew parts for the 180/185 and early 182. These are made of stainless steel instead of the alloy steel Cessna used, and the chain is also stainless. These trim jacks are supposed to be taken out at three-year intervals and overhauled, but very few are EVER taken out because it's a royal pain. I've done a bunch of them and have installed the Cessna access panel kit to make it easier. I used to find those screws corroded badly, a real safety issue. If it breaks in flight you're in trouble, and corrosion weakens it. The McFarlane stuff is WAY better than OEM.
BUT. The blue parts are the parts in the McFarlane kit, along with the stainless chain that isn't shown. What is not included is the little gray mounting bracket with its bushings and chain keeper angle. There are left and right brackets, one of each per airplane. Two jackscrew on the stab. That bracket, last time I checked, was $7,000 for one side and $10,000 for the other, Canadian dollars. I bet they're that much US now. That bracket is hardly any bigger than a golf ball, and is milled out of an aluminum alloy, maybe 2024T3 or 7075T6. They crack, they corrode, and if one of the bushings slips out, it can bend. Nobody makes them other than Cessna. There are a lot of airplanes in use that use them. I am surprised that McFarlane hasn't figured out what the alloy is, had a bunch made, and gotten PMA for them.