Oft times in older tract houses cheap tough trees were planted that would survive anything but they were usually ones that put down deep roots and were water loving.
My plumber wanted $750 to install another clean out and recommend cutting down the problem tree, several more hundreds, or replacing the whole run of pipe. $2000 doesn't seem unreasonable even if painful for the work you suggest.
$20,000, not $2,000.
They would be digging 15 feet down however, through concrete.