Depending on the options, the remodel housings w/trim will cost you around $1100-$1200 each. That price will double (sometimes more) by the time you factor in design, installation, and the aiming/focusing of the finished product. Of course, the artwork that this type of client owns is usually in the 5 or 6 figure range, so its all in perspective.
The installation of the housing is straightfoward, the time comsuming part can be in the adjustment of the lighted area of the art. If the art is a simple square or rectangle, this process is pretty easy using the "shutter method" of light control. If the object is irregular in shape, you will need to custom cut a brass template, which can be very tedious and time consuming to get right.
Either way, the completed project will give you a satisfying sense of accomplishment when you see it.