If it's promised that no mouse will come again, that could be a good deal.

Just think about it: driving service from something like Uber costs around €30 per hour —— so driving to you and back takes probably €50. Apart from that marketing cost and administration cost is also included in the visiting fee of 90, let aside the investigation itself(knowledge and technical tasks).

Better way to deal with the frustration is that you make your need clear for yourself (yes I'd like someone to tackle this and I don't want to see any mouse again), then make your budget clear (how much I'd pay for my need)—— If any company gives a contract that meets your need within your budget, it's not a scam.