“Invoice test” / Experience values

Hello dear community, I absolutely need your swarm knowledge / experience. It is a Smart For Two, built in 2005, gasoline with 45KW, (981 / 001), MC01, with air conditioning The following story (in short form). My starter was demonstrably defective. So I commissioned a good friend to replace the starter. So because the starter was so tight he did not get it and handed this matter over to a car workshop of his trust. The whole prework (stock bar, fenders dismantle, parts of the engine etc.) he had already done before. So the workshop should only replace the starter. In good faith that this did not cost the world then he caused it there. The end of the song was that only the exchange and a new starter cost 78€! The assembly (stough rod, etc.) should have done again my good friend. In good faith that this did not cost the world a lot of VAT. The end of the song was that only the exchange and a new starter cost 78€! The assembly (stough, etc.) should not have been justified for this reason to make this good or to make it completely justified.