Dan, I'd have to agree with Clyde on that one. I'd say offhand that critter is somewhere between 80 and 100 years old. Good chance the guide ways are worn to the point where they'd have to be reworked to maintain blade clearance. Probably more than a little slop in the rotating joints as well, and there's a lot of time and more than a few bucks in material to remake them considering they're likely split bronze bushings.
Then, there's no squaring arm. An absolute necessity on a shear IMO. Easy enough to build a passable one, but more material and more time.
Can't tell whether there's a backgauge or not, but if not, its a major job to build even a manual crank operated one. I've seen some old shears that came with a backgauge consisting of a couple pieces of round stock, a piece of angle, and some brackets to attach the angle to the round and let it slide and clamp after positioning it manually. Not even worth messing with unless you're setting up to cut multiple pieces to the same width.
A set of blades would be seriously expensive as good ones are made from D2. Never bought any, but I'd guess between the material itself which is expensive as hell, plus machining, heat treat, and grinding, I'd doubt you could buy a pair of four footers for a thousand bucks, particularly since these would be custom for a shear that's not been in wide use since you and I were kids.
A quick look on ebay shows a 52" x 12ga Wysong mechanical with a squaring arm and manual crank backgauge for $3295 BIN in PA, and a 6 ft X 11 ga Pearson hydraulic with squaring arm and front operated power backgauge for $4000 BIN in CT.
We've got a 6 ft X 16 ga Wysong mechanical that we used daily for a dozen years in a cut to length line for making ductwork and it never gave a minute's problem. Also have a 12 ft X 1/4" Pearson (made in UK) that we bought in the early 90's when it was about 10 years old, and it has been totally trouble free as well.
Most places doing production shearing prefer mechanicals because they're much faster than hydraulics, but a hydraulic is more "gentle" on itself and also has much less chance of having been used in an operation making a thousand cuts per day for weeks on end. In a job shop, the additional time is inconsequential.
Anyhoo, given what you can spend and get a somewhat modern shear of similar width and capacity, it'd be real hard for me to justify putting any time or money into the one in the pic even if it was a gift and delivered for free.