It may or may not be cheaper depending on what body shop you take it to and the extent of the rust damage, and there is always a chance if rust through again down the road after the repair.
Personally, I wouldn't trust most body shops to do a repair like that. And if it's a good body shop that does restorations and not collision work, they will probably tell you you'd be better off with the new sides.
Buy the new bedsides if you can afford it.


Steve

'49 3800
'52 3600
'57 3100