Photo Matting

Why does it cost so much to get a photo matted? I normally buy them online, but for this coming photo show in San Diego, I just don't have the time to do it myself. I called the local FastFrame here in Noe Valley, and they wanted $46 each for matting + backing my prints to 24"x18". I managed to haggle them down to $40 each, but that's still ridiculous. My normal San Diego FastFrame will go no lower than $24 each, even though just last January I managed to get them to do it for $15 each.

Anyone know of any local, inexpensive, high-quality matting sources (in SF or in SD)?