The OP wrote: "The belt (if sold) would cost around $5, but when the belt breaks you have to buy the entire motor and compressor assembly for $109. The entire compressor new cost $169."
This has become a common problem lately. The original manufacturers have to cut their prices to the bone but they have to stay in business and to do that, they have to rip you off on parts prices they know you will eventually need.
For instance, a girlfriend drives an Accura. The blower motor for the H/AC went out. It cost her $1,800.00 to replace. About the same time, the same part went out on my Chevy pick-up. It cost me $31.00 to replace.
Another instance: I need new shock absorbers (struts) on my Nissan. I have never paid more than about $200.00 for a set of shocks but these Nissan shocks (struts) cost $2,058.00 and the Nissan dealer is the only place you can get them. Nissan has not released the patent on them although they have been on their cars for more than 25 years. Until Nissan releases the patent, no other company can produce them. Nissan is just gouging their customers.
Third example: I had a riding lawnmower. The differential exploded one day. I started searching for a replacement but the original manufacturer was the only place I could get it. Their price was $328.00 for a part that was about the size of a fist. It was two aluminum castings, three steel gears and two steel shafts. Certanly not something exotic or high tech! But, apparently they had found out that this part is fragile and there is no other source for it and thus can rip their customers off. The lawn mower only cost about $700.00 new including the chassis, engine and all other components. I've been in metal forming and machining and know the time and materials involved in manufacturing the parts. It should sell for no more than about $60.00.
These companies lure you in with low prices at Walmart or KMart and then get you on the back end with exhorbitant parts prices. But, don't think it is just off brands. I THOUGHT I wanted a Mercedes and went down to the local dealer several years ago. Saw a sporty model in the showroom and was looking at it. A salesman came over and started putting the sales moves on me. I was standing near the front of the car and said "This headlight is awfully close to the edge of the bumper. If somebody in a parking lot backed into it and broke it, how much would it cost to replace it?" He went to his desk and called the Parts Dept and asked, looked up at me and said "$612.00." I was agast! I had never paid more than about $15.00 for a headlight in my life! Needless to say, My fire to buy a Mercedes was quickly extinguished that day! LOL!
Well, a couple of years later, I still had yearnings for a sporty car and was at the local Chevy dealer. They had a Corvette there and the salesman approached. Remembering my experience at the Mercedes dealer, I asked him about the headlights. Now mind you, these headlights were virtually identical to those found on the shelf at Walmart. His response was "A few dollars." I asked "Exactly how few." He got on his portable Phone and called the parts Dept. They were almost $400.00! I asked him why they were so much more expensive than the headlights at Walmart. His reply was "They are a much better headlight." I asked him if Westinghouse, Sylvania and GE didn't know how to manufacture automobile headlights after doing so for at least 60 years. I saw the same look in his eyes as I've seen in a deer's eyes on a highway late at night. LOL!
It is obvious Chevrolet made these headlights just enough different that they were not a direct replacement for the Westinghouse, Sylvania or GE products sold at all auto parts outlets for around $15.00. For every headlight they sell, they get at least $350.00 in excess profits.
It's not just lawnmowers, tools and automobiles that I see this. Most manufacturers apparently have recognized this opportunity to rip their customers off and have instituted this type of pricing. I've always been associated with business related products instead of consumer related products and I know by experience that if I tried these tactics with my business customers, I would quickly be shown the door. I wonder how they can get away with it with consumers? Are we just incredibly stupid?