The "square head" Regal was a good lathe if not overworked. I believe these may have had hardened bedway "strips" which could be removed for replacement or regrinding.
The lathe in the photos looks to be in OK shape with no obvious signs of abuse. From appearances, I'd guess it was built in the 1960's. I've seen this series Regal lathe go for $2500-$3000 if they had the taper attachment and possibly a collet chuck, collets, and DRO. For this particular Regal lathe with the tooling it has, I'd say $1000-$1200 would be a little on the low end, and $1500-$2000 would be in the right range. Again, as noted by other people who've posted, this is dependent on condition of the lathe, and the region of the US where it is located. In some regions of the US, used machine tools are more easy to come by, and in other regions, it is a desert.
IMO, the Servo Shift headstock is more of a liability than a plus. Too much complex electro-mechanical/fluidic mechanism, and a separate motor driven hydraulic pump to shift the gears. The guts of a Servo Shift headstock are complex, and on a machine that may be over 40 years old, can be problematic. What you are looking at is a good, basic Regal lathe. For 1000-1200, I'd grab it if it were near me. I paid $700 for my 13" x 42" round Head Regal lathe, and while it was fully tooled, it is nowhere near the machine the later "square head" series lathes are. I've seen the lighter "Round Head" Regal lathes go for 1200-1500, so if you can get this particular lathe for under $2000.00, in my opinion, grab it, and consider yourself as having gotten a smoking hot deal if the lathe is in your neck of the woods.
Another perspective is the fact that LeBlond is not making any more Regal lathes, and the ones that are out there are a finite and possibly dwindling number. If you wait for the "right" deal to come along, or squeeze a deal too hard to save a few bucks, you may well be waiting a long time or settling for something less than what you wanted in the first place. A few bucks one way or the other on a deal like this are soon forgotten over the time you own and use the lathe. Better to think you may have overpaid than to miss out on buying the lathe and winding up regretting not buying it.