Well, if I have a big job, I'll order the parts online in advance and generally score some huge discount. My local shop will install my parts I supply.
I just had a bunch or am doing a bunch of repairs/maintenance on several vehicles. But I'm aggressively getting parts bought and work done before serious inflation strikes so my vehicles are all tip-top for the next 10-20 years of ~1000 miles per vehicle per year driving, which is about what I do. I'm trying to really get ahead of the curve.
1998 Ford Explorer, 4.0L SOHC with 203k miles - recent work done: manifold and valve cover gaskets, belts, hoses, flush and fill radiator, fuel filter, thermostat, sensors and seals as needed, etc. I also personally changed plugs and wires and Cleaned Mass Air Flow Sensor, Clean Throttle Body, Replaced EGR with new, oil and filter change. I've got about $1000 into the maintenance between my shop ($900) and me ($100) and it's almost tip-top with a minor issue still remaining.
2004 4Runner (4.7L with 202k miles) is tip top, just had major work done - Timing belt & serpentine belt (both were replaced with new but old ones looked excellent with at least 100k miles on them), water pump & gasket, camshaft seal, seals, gaskets, thermostat, PCV, timing belt idler & tensioner & pully, flush and fill radiator, fuel pump and filter, EFI relay. Parts and labor ran about $1400. Different shop did CV axle shaft replaced, flushed power steering and ATF, and new front rotors ($900). Another shop (best transmission shop in town, very honest) fixed a leaking 4WD transfer case, luckily cheaply, only about $50! I also did an oil/filter change. So about $2300 to address everything wrong and perform all needed maintenance in the last 18 months.
I'm doing likewise with my two other Tundras, so expecting similar costs. It's critical maintenance, but also important to do it now as I expect massive inflation is upon us, and parts are getting or may get harder to source as used cars get more common b/c nobody can buy a $80,000 new car or truck...
I have two Ford Panthers and have some various routine things to do but nothing too major. I expect less than $100 in maintenance items for each and I already have the parts and will do these myself.
At the rate I drive, probably 5000 miles annually between 7 vehicles, I am hoping that once I get ahead on all these items I'll be set for the next 10-20 years of driving without major repair bills...