Well, I wouldn't be concerned with the difference in sensor prices, as the new engine would've cost thousands of bucks. You still made a smart move by checking it out. Same with checking out the engine check light. Some sensor faults, if left can cause engine damage and other sensor damage in the longer term, so a quick check is good insurance.
Same goes for regular oil changes. A lot of people let it go too long. Oil sludge builds up creating blockages or restrictions in the oilways and can cause catastrophic damage. My Mother in Law (!!Sigh!!) missed 3 change intervals. She said the oil was leaking out enough not to bother as it got sort of replaced every couple of months. Eventually it started clattering much worse than a diesel. When I took off the rocker cover it was dry inside....Oh Sh**!
I took the cam and rocker shafts off and they were completely blocked. Luckily the cam and rocker gear were just OK, but had to replace hydraulic lifters and some valves as they had no oil supply, collapsed and hammered themselves to death. Also had to pull off the sump, clean pickup pipe, pump and other oilways. Probably lucky no firearms in the house. Would have had to shoot the car and put it out of its misery.............
The upshot? She saved $45 x 3 = $135 on maintenance, but repairs were around $500. Would have cost much more for a mechanic to do it.
Seriously, regular maintenance and preventive action saves a lot of headaches.