You should compare like with like, that is fair - so you should compare your salary after 5 years at uni with the salaries of investment bankers, some of whom also spent 5 years at uni.
I don't know how old you are, but to compare the physical side of work of a poor sod who is bent double to fix your valve (digging the road, tiling the roof) at age, say 50, to the genteel physical endeavour of a teacher/officer worker is wrong. If anything, they should be charging more.
There was also an excellent comment here - about tools, driving to/driving from and being self-employed - no paid holiday, no paid paternity leave, no paid compassionate leave, etc. no luxuries which full-time teachers somehow take for granted.
But I see what you are saying - in my opinion, teaching is the most important job in the world, not just subject teaching, but brining up new generations the right way. Of course you should be paid more, of course you should be afforded more respect, but we should leave any comparisons with physical jobs out of it, I think.