Fixing stamped concrete or pouring it new
If the slab is sound and only looks faded or dull, a good cleaning and a fresh coat of sealer usually bring the color back, and that's where I'd start. Once it's cracked through, sunk or tipping water toward the house, I'd replace it, because the trouble sits in the ground underneath and a patch on a stamped pattern rarely matches. I'll tell you which one I'm seeing when I walk it.
What sets the cost of stamped concrete
Size comes first, then whatever has to happen before the pour, like breaking out an old slab, digging out soft dirt and hauling in base. A busy pattern, a border, a second color or a set of steps all add labor on pour day. When a budget's tight, people want to cut the base because nobody sees it. I'd trim the pattern instead, since a border can be added later and a slab that settles can't be fixed.