How much does it cost to deal with there's a root wrapped around the base of my tree?

Nothing here prices like normal tree work. The corrective job is hourly excavation with an air tool plus arborist time, driven by how deep the flare is buried and how much soil must come off, not by tree size or canopy spread. Hardscape multiplies it: a tree in a sidewalk cutout, tight against a driveway, or ringed with landscape fabric and stone costs far more to open up. Diagnosis alone may require a partial excavation just to see what is down there, so expect an exploratory charge before any firm quote. If the tree is past saving, cost shifts to a normally priced removal, plus correcting the planting practice so the replacement does not repeat it.