The guy who installed ours was very open about his earnings, he was on £45k salary plus £30 per install, he said he could easily do 3 each day. He was a fully qualified local authority trained spark.
How strange someone would gloat about their income, yet only get £12-£15/ph installing a charger!
I charge £90 for a EICR on a one bed property safety cert and certainly wouldn’t be signing my life away as well as doing the manual work for £30.