Just to share a similar story with my Nissan Pathfinder: After about 10 years or so, a common problem with these things is the failure of the IACV (Idle Air Control Valve).
The engine dies (won't idle anymore) but worse, the failed IACV also takes out a component on the ECM. This happened to mine.
Dealer cost is $1,400 for a new ECM, $400 for an IACV, plus labour.
Like you, I learned on a Nissan forum how to remove the ECM, and send it out for repairs (cost was like yours: $150).
Still had to buy a new IACV, but they can be had at parts stores for half the price.
An hour or two in the driveway, and the truck was fixed.
The biggest PITA was doing what's called an idle relearn. The repaired ECM and new IACV have to get in sync with each other, and it's a convoluted procedure.
All this to say that if you're mechanically inclined and interested in this stuff, you can save a lot of cash on repairs over the life of your vehicle.
It comes down to convenience, as well, for me. If I can possibly get to the dealer (tow truck included in warranty...), I can get a loaner and let them suss out the issues in their due time. That means I can still get to work, etc. A few shifts that I go to vs. not, and my warranty is paid for. Even forgetting the parts/labor aspect.
Also, I did all that stuff in highschool, college, and my first few years. I don't really find pleasure in it.
-Did my own clutch hydraulics on the WS.6
-Did my own shocks on my P71 Crown Vic
-Did my own PCM change on my Jeep
-Did my own water pump on my Mustang GT (2 or 3 times...)
-Did my own window motor gear fix on my 1995 Trans Am
-Did my own valve cover gasket on my G20
-Did my own ignition switch on my G20
-Did my own oil changes for years
-Other stuff I've forgotten, including tuning IAC's, FP regulators, and all sorts of stuff with intake/ignition/exhaust systems
I simply view having someone else do this for me as just another form of luxury, like cooled seats or a NAV system. Is it necessary? Will it save money to 86 it? Okay...but luxuries are nice, or we wouldn't even be on this forum. We'd be on the 1980's Subaru forum figuring out how to keep our "bare necessities" running. Because buying a 20 year old Subaru or something is the ultimate cash-saving move. $1500 out the door, $1500 in parts, and it's G2G for a long time for $3K and some of your time, AND you can use liability insurance only on it then, too, etc. But we all must agree that SOMEWHERE, each person will draw their own line of "diminishing returns" and "level of satiety", per my econ 101 professor some decade and a half ago.