I justs recently replaced a built in GE Microwave's magnetron and diode for around $75 with parts off of Amazon (it was 5 years old). To replace the Microwave would have cost me around $800 and to call a repair person would have been about $250.

Thanks to youtube and about 30 minutes of work it is working like new again. These days I fix everything myself. Appliances, cars, electronics, furniture, etc. I also try to buy quality instead of disposable but that is getting harder every year.