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!