The expense to change timing belts is a common question here. I change the timing belt myself on my early 90’s Corolla, but found it to be a difficult job. Not the actual changing of the belt. That’s no more complicated than lining up the 3 numbers on a combo lock so it opens.
What was difficult was supporting the engine and removing the front engine mount – you have to do this to get the belt into position.
The bolts to remove the engine mount were on so tight they tended to round over instead of letting loose like they should, and when the engine mount was removed, the engine twisted slightly, which made it difficult to re-install the mount. I supported the engine from above and from below, but still had much difficulty w/this. And removing the bolt that sets the tensioner was difficult too. It wanted to round over.
Anyway, it seems to me the timing belt path could be re-designed in a such a way that you wouldn’t need to remove any engine mounts. All you’d have to do its remove the timing belt covers and change out the belt. A 20 minute job. With time for beer break.
Are the engine designers just plain lazy, and don’t take into account the amount of work needed to change out a belt? What do you think?