Well, there are prostitutes who get £5,000 an hour (I am not one but nice work if one can get it..).
It really isn't a question of your training or the importance or difficulty of your job. It's a question of how much someone needs you to do it.
I totally agree that teaching is unbelievably underpaid. It is a really demanding job, and really important. However, unless you go and teach English in Dubai, or work up some popular you tube channel, you are always going to be subject to UK market rates. Online tutoring is a bit better but still variable. Managing a class, especially of children, is a very big job and the money just doesn't reflect the skill, input and responsibility. Yes, you would get more as a dustbin lady.
With tradesmen, the thing is that they can do critical stuff that we all need. So they can charge a going rate, and will modify this according to how much they think they can get. A rich and/or pliable client will get charged more. Of course.
£75 for the light pull is a bit OTT. The pull itself costs about £1.25. If he just replaced the cord then that is a 1 min job. If he unwired the old one and connected up the new one well then that's very specific skill, so you pay for that skill rather than the time.
With a lot of tradesman work, it is about the job being done rather than the time it took.
You chose to pay a neighbour cash so you can't complain about it really. £270 for a day's work is quite high for cash but if he was doing electrical work then maybe that's why. If someone else did the electrical work then of course you have a min. call out for them to come to you.
Next time shop around if you don't like the price. Someone else will usually do it a bit cheaper.