Looks good mate. For these types of things I often prefer to see the weld left on, grinding it out in my opinion makes it look a little unfinished. That is of course unless you are going to paint it. Money wise, wouldn't have a clue.
Agree the grinds look ugly, would have put the seam underneath too on the RH armrest. Diresta makes this stuff look easy but somehow the proportions and subtle angles (on the legs for example) make or break the design.
Looks good though. I would have thought £80-£120 depending on how the final item is finished.
The positives are it's a good heavy bench and looks good whilst new although also agree with the others re the grind markings
The negatives are personally I dislike box section for garden furniture, painted treatment tends not to last and rust will soon appear from inside and especially where it touches the ground, also unless it is a trick of the camera the left hand front leg looks out of alignment by a fair bit.
Value? whatever someone is happy to pay, the problem is the market is flooded with garden furniture from the cheap and cheerful to the insanely expensive, there is a market for artistic stuff that can demand high prices but it has to be very 'one off' in appearance and to a high standard of design and finish.
If you are thinking of making and selling them you may find what you can get won't make it worthwhile considering the material, consumables and your time, especially if run on a legal business footing with liability insurance and everything else that weighs a small business down.