Hi Terry,
There are as many ways to build canvas tops/enclosures as there are houses; you can run the gamut from a standardized 'spec' home to a full-blown 'custom' model.
The King Marine camper canvas is a good base for comparison. King has the patterns for the CD22 and doesn't have to custom fit each boat and they have dedicated seamstresses; the pattern and installation folks don't do the production sewing. This all helps keep costs down. The basic King camper canvas with aluminum bows, two removable side panels and one removable back panel is $960. Going to stainless bows (a good thing IMHO) adds $155. The quality of the work done by King is very good; far surpassing the typical "factory" top on most boats.
The shop that is doing our custom canvas work (when 'standardized' versions aren't the customer's choice) adds many features to the top which we designed in..all stainless framework, quick release bow fittings, which are $80 more on the King top (to facilitate removal of the framework), solid struts to tension the top and hold the framework up out of the way when the top material is removed. A zipper across the forward end of the top material to facilitate dropping the top (or accessing the cabin top) without having to slide it completely out of the awning track to one side. The side panels are split into 3 sections so that you don't have to unsnap anything to get in and out of the boat (something I hate with cold fingers and full hands); and the zipper in the top (which zips toward the center) means you don't have to duck under the low sides. The individual small panels stow easier and you only have to unzip a small section (which is removable) to enter or exit the cockpit. The back curtain is in three sections; the center section matching the width of the motorwell with a narrower section on each outboard end; each of the three sections is individually removable. This allows access to the motorwell or to the lazarette lockers without undoing a 1-piece back curtain. The curtain doesn't snap at the bottom because it's difficult to reach snaps that are on the outside from the inside; instead the curtain is held with bungee loops which fasten onto lashing hooks. This is very easy to do from inside and pulls the curtain nicely taut when hooked. The clear vinyl material used for the windows is .030 pressed and polished sheet material rather than the more common .020 rolled clear vinyl; it has much more clarity and doesn't allow the curtains to move around as much in the wind. The clear 'glass' in the back curtain drops all the way to the top of the motorwell so that you can see the motor(s) from the helm seat. All-totalled you have 9 small panels to stow (the forward one on either side being really small) rather than 3 large ones when the side and back curtains come off (although they could be left zipped together). Each of the panels is individually and completely removable so when you don't want one you can stow it away rather than having to roll it up on the side or flip it over the top (where the wind usually flips it back down). Once the side and back curtains are removed the top itself unzips and comes off in a matter of seconds and the framework remains standing in place and does not drop into the motorwell.
This is more expensive at $1500; whether or not it's worth the extra expense is at the discretion of the buyer. I think it's an awfully full-featured top for a very fair price. [As a side note: this price is direct from the Canvas Riggers...we don't sell them per se and there is no markup on our part.]
So depending on the complexity of the design, the quality of materials used (the top/curtain material it self, the clear vinyl, the zippers, the snaps, the binding, the bows (framework), and the top fittings (eye ends, jaw slides, supports, etc)), the $1200 you were quoted seems right in the "ballpark". This is a very labor intensive thing to do (I can vouch for that having done it myself professionally); you can bend some aluminum tubing in the shop (stainless is a different deal) and sew up Sunbrella on most home sewing machines but most folks will be totally surprised at just how long it takes to pattern the thing and then sew it up.