Geeze, that seems expensive. I had to replace my sewer line several years ago. Money was really tight. I called ARS and got a $88 drain clean, as part of the deal you have to let them scope it and give estimate. They wanted $4000 to replace my sewer line, about 30 feet. I rented an excavator and went to pipe supplier......did it for less than $500 and a days work.We are being told 4k. Which seems steep to dig a hole, cut the pipe and install a Tee/vertical. They also need to snake and scope it, so It hopefully includes that.
You have to keep in mind though. When a contractor bids a job, especially digging....you just have to allow for "happenings". I have had jobs that I bid, and everything went fine and I make good money, but you are always 1 mishap or mistake away from losing money. If I charge someone $500 to put a $1000 window in, and I finish in 2 hours, I do well. But if something happens and I break that $1000 window, I just paid to replace the window.