Repairing or replacing decorative concrete
If the slab is solid and only the top looks worn, a good cleaning and a fresh coat of sealer can bring it back, and that's where I'd start. When it's cracked through, sinking or holding water against the house, the trouble is usually the base underneath, and anything laid over it inherits the same problem. That's when tearing out and pouring again on a dug-out, packed base is the money better spent.
What shapes the cost of decorative concrete
Size is the big one, then the finish, since a detailed texture takes more hands and more time than a plain broom finish, the light dragged texture that gives shoes and tires some grip. Tearing out old concrete, hauling it off and fixing soft or badly drained ground all add to the bill. When budgets get tight, people want to trim the base work because nobody sees it on day one. I'd rather trim the finish, because a fancy top over a weak base usually ends up cracking and settling anyway.