I got a $1500 quote to replace a stuck thermostat in my car from my local mechanic. After some Youtubing I was able to replace the part myself with $150 in parts.

I got a $5000 quote to fix my AC 2 summers ago and no amount of Youtube was able to help me DIY a fix.

Maybe in the long term there will be more HVAC techs than auto mechanics. Somehow I don't think that's likely.