Dual lowlights?

I saw a picture of hair that had a few different shades of highlights in it that looked really good, and since I have really light blonde hair I wanted to do that with lowlights. Anyway, my question is, would a salon charge me for 2 lowlight processes? Like if I wanted 2 different shades, would they just charge me twice? I mean if you think about it, instead of having 2 full treatments of, say, ash and light brown, i'd be getting a half treatment of ash and a half treatment of light brown.