Let me start off by saying that we do ALOT of sewer inspections. I am a firm believer that you cannot honestly judge the operation of a system if you cannot see it, and this especially rings true with the sewer line. Most of the vent pipes and drain lines in a home are hidden from visibility. This causes most inspectors to just flush the toilet, and if the water goes down all is well, right? Well, no, not really.
I was amazed by how many issues we started finding when we began doing #sewerscopes. Just in the past week we found clogged up vent pipes, cracked drain lines, massive offsets, and tree roots.
Depending on the sewer line issue, you can assume most repairs will be around 2-10k depending on how much line has to get replaced, what has to get dug up, and if you have to replace concrete, or driveways.
In short, when you're shopping for a home inspection, make sure to inquire about sewer scopes. It might cost a little bit more upfront, but it will pay for itself 10-fold.