I checked some list prices, and they're a substantial price of the fridge itself. Some site said $200-$450 to replace one, another said the part itself is $100-$500 without even including labor. At those prices, I can see why people might just buy new. It's also something most people would want to hire a professional for; refrigerants are not good to inhale, and this needs to be air-tight.

I would also hope that most of them get refurbished. It's pretty hard to just "discard" a fridge. You have to call someone at the city (or GoodWill), and I presume they sell those to refurbisher. They're worth some money.

So I think in reality, it goes to a refurbisher who fixes it, then sells it to someone else who replaces and even older fridge. So the fridge that actually ends up in a landfill might be a 1960s deep freeze. The same idea as used cars.