We bought our own roto-rooter from Lowe's about 10 years ago and did preventative drain cleaning a couple time a year. Electric 1/2 HP model with 100 ft snake and a couple 'knives' was under $250.
Third time we used it we were saving money.
Since then we have added 'horse trough' settling tanks and no longer need the drain rooter outer thingee.
Simply clean/scoop out the tanks twice a year, add kitty litter to the solids and dumpster it as a solid.
Lots easier than getting out the jackhammer/backhoe in the worst case scenerio!
~Kitson