I understand what you are saying, "you get what you pay for", but this is not some permit to fly maintenance job, this is a certified EASA, and the job has to comply within certain parameters.
I..e. if it was a permit to fly annual, like LAA (Light Aircraft Association), you can have almost anyone do the maintenance, and of course in this scenario if yo pay very little you may get a "monkey" to do the job, but in the EASA type maintenance, only approved maintenance operators can perform the work, those it is more likely that wherever you get it done it doesnt matter...
So my plan was to shop around, as the EASA certs are expensive, and why not get a cheaper deal if you can ?
thats my 5 cents on the subject.