The supermarkets rip everyone off because they want to maximise profits for their shareholders.
The others you mention tend to be self employed. Looking at it from their point of view. They will have worked hard(long hours etc), and have to cover overheads, not get time off or sick pay when they are ill. They probably feel justified in charging customers what they think they can get away with!
Some of the professions you mention vets, solicitors need degree and often other qualifications. Nowdays as well as running a business, paying a mortgage, childcare, maybe school fees, They have student debt to pay off. Things are not going to get better. We will have to pay for their university education in the end!