The last one I made had to fit a somewhat narrow space next to the garage door. So it was custom built to my own sketch using used 2 by 6 lumber from a discarded deck. Overall cost virtually nil. Good and solid using screws to take engine parts. A four by four leg from an old gate-post at the end not supported by walls is under the corner mounted vise making it much safer to beat on something held in the vise. Shelves above are high enough to allow something 24 inches high to be worked on on the bench.
Benches are very much what you need them for. No one size/type fits all!
Completely different application downstairs; electronics bench is two used 6' 8" (13 foot total) doors, end to end, supported on a frame made from discarded steel shelving angle. No pounding on that one but fair amount of space with shelves not too far above for test gear.
Respectfully suggest that if anyone is capable of making things 'on' a work bench it would be a good exercise to build the bench itself as starting point.
A third bench was built quickly some 37+ years ago, while building this house, using scrapped wood from some shipping pallets. It now needs some repair and upgrading.
A fourth bench was found dumped; about four feet long, quite low but a convenient height for some tasks, it had been ingeniously made of pieces of cut off doors. Quite sturdy it mounts our largest/heaviest vise.
So; conclusion! Decide what the bench will be used for and then build it to that requirement. A gardener's potting bench need will be a completely different thing to that of an electronic enthusiast's!