Question on main sewer line backing up every few months

I have determined via camera inspection that I have a dip/belly in my main sewer line from house to city main.
I saw water sitting in this area via the camera it is @ the 17 ft mark and goes to about 31 ft. The whole run is 46 ft cast iron.

I was quoted 6k to replace that section which does not include replacement of landscaping/sidewalk and grass all which will have to be torn up.

The house was built in 1950, is it common for these runs to have these bellies in them, more importantly can I live with this if I do preventative maintenenace on the line every month or so? While the pipe is not clogged, there is standing water in the belly and some slude/grease.

Secondly, is having the pipe sewer jetted a waste of time or do you think it may help. While I can snake it myself w/ a power auger, I Am never really actually giving it a good cleaning/scrubbing like the hydojetter will do. This will cost me 900 dollars to have done. I am hoping this may help the situation because spending 6-8k right now is just not possible.

your help is greatly appreciated,

regards,
harvey

How deep is it? I can't imagine that much money to expose 14' of pipe and straighten it out.

You are never going to clean it squeaky clean. You can clean it yourself much cheaper and do it periodically. you were quoted too much money.

What material is the main?

Molo

the whole run is cast iron 46 ft.

thx,
harvey