I wouldn't disagree with any of your observations on my likes and dislikes, Octy. I do like to get my hands dirty from time to time and I do all sorts of DIY, learning (generally stuff of quite limited use) along the way is all part of the fun for me.
If your OCD extended to following Toyota specs you would have replaced your engine oil and filter 13 times, had 13 Hybrid Heath Checks, replaced your brake fluid 10 times, your pollen/AC filter 10 times, your air filter 5 times and your engine coolant once or twice in addition to the bits you mentioned. I'd hazard a guess that you've gone through a fair few litres of screenwash and possibly replaced the wiper blades given your desire for spotless windas, also. Add all that up and, employing mechanics to do the work, I doubt you'd get out for much less than the 1.3c/kilo my 8 year old MKIII Octy has cost to maintain since I acquired it. Then there's the Capital cost... I guess you're looking at c.€3,000k/year for the bought new Prius whereas my second hand Octy works out at c.€1,700/year... assuming both cars last until they're no longer acceptable to NTA under current regulations.
IIRC, NTAs excuse for complicating age extension provisions beyond belief was more to do with the Suez Canal than COVID '19 anall - pointing to a perceived shortage of cars. Obviously a shortage of anything results in higher prices - Free Now's surge fees being a case in point. The price of cars, in particular second hand cars, has continued to increase and perhaps, most relevant to NTA, Brexit has significantly increased the price of UK import second hand converted cargo vehicles, the very vehicles from the very source it identified as being key to increasing WAV provision when it changed relevant vehicle standards to accommodate the same. Hence, the WAV providers are certainly justified in seeking further extensions. I feel justified in wanting an extension simply because prices of cars haven't decreased at all since some of my competitors were granted an extension. A level playing field is all I'm asking for!
Having said that, Watty also makes a fair point. I'll be picking up a hire car in foreign climes later today. If they were to offer me the keys to a 3+ year old clapped out Prius they'd be told where to shove them... albeit employing somewhat more polite diction.