Found these old welders for sale, any know what's a good price to pay for one or whether or not it even worth pay for ?

Hello everybody, I work as a boilermaker servicing Various sites daily. My duties vary form Welding (multiple processes) to brazing, to masonry ( Refractory), to threading to fitting to plain old simple mechanical . I also spend a lot of time sharing Welding education with peers and my kids, as well teach a boilermaker apprenticeship program with NCCER.
WTT has always been a go to pointers, but now welderskills is triple up grade if not more with all the different collaborations.
Thanks