Totally agree! Do some mystery shopping.
Set up an email account (non related to yours) and send out a request for quote based on scope of works (SoW). Make sure you are quite specific in your quote. You can always say on the email you are flying out, and can they provide a rough guide of costs based on SoW by email as you can't phone.
It's a great way to find out how others sell themselves and the prices they offer. Send the email out to a couple of companies first, as you may need to refine based on feedback.
Don't worry, you're not doing anything wrong. Companies have been doing this for years.