Replacing cast iron sewer pipe. How big of a job is it?

Plumber found a broken sewer pipe. Been quoted 16k to replace. Slab on grade foundation. Plumber says he needs to dig under the house. Would it be easier to cut the floor and go from the top? The septic system was just redone and now this. I understand getting the poop out of the pipes is important but damn. 16k seems very high. Is there a liner that can be installed instead of replacing the whole pipe? Or any other alternatives?