Septic fields, am I being ripped off?

here's what I can tell you. I've recently dealt with roto-rooter and redi-rooter companies and my suggestion is RUN! My septic system backed up due to what I found out was a collapsed mainline right at the entrance to the septic tank itself. Before this I had no clue about septic systems other than they have a tank that hold the poo... Both redid and roto told me I needed a whole new drain field because it was all clogged and/or collapsed. The evidence, per them, was the level of water in the tank. I had a pump truck come out and lucky me he was a stand up good ole boy. He said the tank was perfectly fine, and actually in good shape considering the age and use I put to it the last few years.
As said before, this is an area of the home that you do not want to go the el cheapo route. spend the money on a good and proper system. Have them show you how they know the lines have collapsed. Which BTW, if the lines have collapsed and its not backed up, it isn't that the soil is so good, but that the soil has probably washed out. From what I have been told. 20k is way out there...find another place that will do it.