$4300 actually sounds quite reasonable.....
But there are questions that will be asked --- for example, is there only one line?
And where is it? We've heard of situations where a line was actually going through someone else's property and as such involved a little more work (and agreement from the neighbor)
How long is the line from the house to the curb? I had a client whose sewer line was 100 ft long. The video showed that it looked fine, and the sellers were hopeful that it will pass the city's test. At around 90 ft....it failed. So they had to replace the line.
What kind of sewer line are you looking for? Trenchless is another option.
So there isn't one answer to your question.....best that you get estimates from at least two plumbers. YOu may be surprised at the difference.