It is easier to keep a vehicle with minimum electronics running for longer. All the electronic gizmos fail over time due to corrosion, gradual breakdown and increasing fragility of PVC or other plastic parts including the coating on all the (MILES) of wires themselves.
After all that, there remain all the mechanical failures that a vehicle with no electronics can also have. People seem to forget that, even with 5000 sensors, your chassis can still crack or a radiator hose can still burst etc etc.

If you buy a structurally and mechanically sound base vehicle such as an 80 series (running well and not rotten with rust, NOT necessarily mint) and throw 10k at restoring it, you will have a very tight vehicle indeed. 15k for a 100 series that cost 50k+ new means someone else already got 35K of use out of it, its far from new.

Its beyond me how you could spend 40k prepping a vehicle. Where are these people going, the moon??

With an 80 for example;
replace the rad, hoses, water pump and flush the cooling.
service the front and rear axles and the drive line.
service the engine.
put decent suspension on it.
put decent new tyres on it.
stick on some form of a bullbar (in case you hit wildlife/livestock).
throw a few jerrycans in the back for diesel and water.
Total cost of doing all this with proper Toyota parts except for the suspension, tyres and Bullbar, 5-7k. Labour, I would guess another 2/3k; but make sure whoever does it knows what they are doing.

Everything else is only toys: roof tents, shower systems, fridges, split charge systems, on board dvd player, built in hot tub!! ........
If you were on a bike you wouldn't have any of the above and you wouldn't die for the lack of them

When you look at these 40k spent vehicles, you wonder where the money was spent.... toys usually..... and then you wonder how much of the worthwhile stuff was done properly (use Toyota parts, NEVER rubbish pattern partsfor essential stuff, they are cheap for a reason usually)

Instead of paying someone to do all this, learn to do it yourself, even if you have to pay someone to teach you a bit of it. The factory service manuals are available for free in .pdf online, more basic manuals can be bought on amazon etc which will be easier for those with a non mechanical background (the FSM's assume you have a reasonable basic knowledge of mechanics). That way you'll know it was done right and if anything does break you;ll be able to diagnose the problem and most likely be confident fixing it.

All the above applies if you buy a 60 series and 80 series or even a 100 series. bi er