A warm welcome to Mac-Forums, Mihaela, and thank you for posting.
To be perfectly honest and frank, the cost is well within professional fees for such a service.
If you were to go to an independent professional lab for data recovery, the cost could be anything up to 10 times that amount.
In many ways, you are fortunate that you got these files back. It is a credit to you that you immediately recognised your mistake rather than waiting days or longer, by which time they could have been overwritten.
You asked for an opinion. Maybe mine is not what you were hoping for. At the end of the day, how important are the Files? Your call.
BTW, which Data Recovery "apps" did you use? No need to say if you'd rather not. But most of the respected ones charge on a "pay if we find the data" basis. Some charge up front, success or not.
Ian