i don't know how much it would be, but do know from watching tv the stamped pattern is rather labor intensive...they have these "rubber mats" that make the pattern, but it's pick up move stamp, ect...during the process is when they put this powdered coloring (at least on this old house, lol) of course your location adds to the cost... i'm guessing with sun, rain, i assume you get, some sort of sealing would be advisable...why not check at city hall and see what the local building codes are...who knows some of your old cement block if in good enough shape, might be worth something?

I agree, your patio looks great. Here's the thing: You can't expect the contractor to match a color in a photo like that. The photo isn't accurate, and there's no way that he could say with any confidence that your patio will look like the one in the photo -- even if he knew exactly what stain was used. You have a very attractive patio. The coloring of your patio looks more like slate and less like the stamped concrete of the original photo. They did a great job!

We had a similar situation where a concrete pad for a set of steps was poured against the front wall of the house, to above the concrete foundation level and above the sill plate that sat on it. There was originally flashing to keep water away from the join but over the years it corroded away and the water rotted out the sill plate. That and a couple of other pieces of bad design rotted out the entire corner of the house, which we had to have rebuilt. While you might keep an eye on the flashing and caulking, how about future occupants of your house? Will the knowledge that this must be done get passed on, or lost? Caulk is not a long term solution. One possibility for a long term solution might be to remove the concrete steps entirely, while keeping the patio, and build wood steps from the patio up to the doors.

That your existing concrete is in good shape is key. Any crack in it would transfer through to the new material. So long as you create proper finish levels, you should be in good shape. Stamped concrete can look terrific. It's biggest drawback is the color not being integral to the slab, but just surface treatment. This is really no problem unless it is subject to harsh wear, which in this instance is probably not going to be the case. If the surface gets a chip or gouge, you'll see near-white concrete below. In most residential situations, it doesn't get that harsh of treatment.