Concrete Deck Post removal

Hi: I am new to this forum. We have recently removed a 24" high wood deck to replace with a set of stairs and a patio . All the wood has been removed and we are left with 8 concrete sono tube forms sticking up from the ground (clay based). They are approx 3 - 4 feet deep into the ground. How does one go about removing them? Do we cut them off at the base? Do we jackhammer them out? Not sure. I got a quote to get a bob cat in to remove and dispose of them and the cost was exorbitant? ($600 for the bobcat & removal - & $400 for the bin and dispose).

Any help or suggestions would be most appreciated.

Stuck