Don't really know since a pro will likely already have his dyes. It wouldn't take but a few drops mixed with some lacquer or DNA. Of course, he'll still charge for his materials and time for sure. But, to me.... it would be worth it. As for the difference between the veneer or face side or doors being different, there won't be a lick of difference sprayed with a dye stain I wouldn't think. Think of an opaque stain you might use on a cedar deck or siding. It covers the grain up some, but you can still "see" the grain through the stain. Not as clearly as a penetrating stain, but.... it colors the entire board very evenly. So whether you're spraying plywood, veneer or face wood, with a dye stain, everyting comes out very even and clean looking. That is, if you're a pro that has the right tools, knows how to use them and of course, the experience. One of the problems with spraying dyes as stains or even very light shades as toners over stains, is you can end up with stripes. That's where knowing what you are doing with the proper equipment will separate a cabinet pro from a DIY'er like me.
I thought the gel stain approach might work, but for Sherry, obviously it didn't. Maybe she got everything too smooth going to #180 (I would have stopped at #120 or #150 for certain so that I could get something a little rougher for the stain to grab). But, either way.... the gel stain approach was at least worth a try IMHO. You can buy that stuff in half pint cans so I figured it was worth it to see. I would have tested a bunch to be certain before I ruined my entire kitchen though. But, hind sight is usually better no?