For many small appliances this is true plus they weren't made to be taken apart to be fixed.
For larger appliances there is a law of diminishing returns. I fixed the dryer three separate times, replacing the heating coil, the drum rollers and the drum belt all for under $150 total. The dryer is 25+ years old and owes it's continued life to EBay. A new replacement would cost way more than the original even with repair costs added.
I just had a repair technician come and take a lot at my washer — which has started to make some unusual noises. His prognosis: “The good news is that it still works, and using it while it’s making these noises won’t do any harm. The bad news is that I can’t fix it because it needs one key part that isn’t made anymore. The better news is that you wouldn’t want me to fix it anyway … because the cost of repairing it will be more than half the price of a new one.”