If your grandmothers plumbing is costing that much, and requires the use of a backhoe, its most likely tree roots in the stormwater and/or drainage pipework (stormwater = pipework from gutter to downpipe to street kerb outlet; drainage = pipework from toilets, showers, basins etc to septic tanks, holding pits, trenches and/or city sewerage). They get in the joins between the pipes, and freak out and grow like crazy because of all the water, cracking pipes as they get bigger, and clogging them so nothing gets past and you get water bubbling up in the yard, or worse, raw sewerage. If you catch the problem early, you can use (what we call in Australia) an electric eel, which is a big coil of steel that spins and rips out the tree roots in a big rope like this:
Catch the problem too late, and the tree root blockage gets so heavy that the eel can't get in there to grab purchase, and the pipework needs to be excavated, cut out and replaced with new.
There are stop gap measures to prevent having to dig up the garden etc and replacing all the pipework, like running the eel through the pipework every three to six months to clear the new roots that -will- grow back, but leaving it that long means more tree roots will make more penetrations, and more pipework will be damaged, which means more pipework to be excavated and replaced.
Still, $2000US sounds really expensive (that's about double in Australian, i think - or once and half again... something like that), so the pipework under the slab of the house (or cellar - they're popular in the US, or so the TV leads me to believe) or a vast majority of the stormwater/drainage pipework may be blocked and/or damaged. I hope your grandmother shopped around for some prices, because there are shonky plumbers out there who, in these desperate times, will jack prices up like crazy on quotes just to cover their overheads.
Also, and this is from personal and professional experience, getting big jobs like that quoted more often than not ends up adding close to 10-20% to the total bill, and while it's scary to say 'Just repair it, please', you can save money by getting the work done and receiving an invoice for work done, rather than work quoted.
Also also, your grandmother might consider having some trees/plants removed to prevent this from happening in the future, and also having a plumber come around once a year or so to check all the pipework with a drainage camera to make sure the problem hasn't occurred again.
super long comment about plumbing is super long, and all about plumbing
Catch the problem too late, and the tree root blockage gets so heavy that the eel can't get in there to grab purchase, and the pipework needs to be excavated, cut out and replaced with new.
There are stop gap measures to prevent having to dig up the garden etc and replacing all the pipework, like running the eel through the pipework every three to six months to clear the new roots that -will- grow back, but leaving it that long means more tree roots will make more penetrations, and more pipework will be damaged, which means more pipework to be excavated and replaced.
Still, $2000US sounds really expensive (that's about double in Australian, i think - or once and half again... something like that), so the pipework under the slab of the house (or cellar - they're popular in the US, or so the TV leads me to believe) or a vast majority of the stormwater/drainage pipework may be blocked and/or damaged. I hope your grandmother shopped around for some prices, because there are shonky plumbers out there who, in these desperate times, will jack prices up like crazy on quotes just to cover their overheads.
Also, and this is from personal and professional experience, getting big jobs like that quoted more often than not ends up adding close to 10-20% to the total bill, and while it's scary to say 'Just repair it, please', you can save money by getting the work done and receiving an invoice for work done, rather than work quoted.
Also also, your grandmother might consider having some trees/plants removed to prevent this from happening in the future, and also having a plumber come around once a year or so to check all the pipework with a drainage camera to make sure the problem hasn't occurred again.
/end super long plumbing comment.