Cold waxing doesn’t really work as it only puts the wax on the surface and this quickly gets removed, the wax needs to get into the base of the ski where it will remain much longer, also cold waxing often affects the skis performance as most people tend to leave too much on the ski.
A wax and edge should cost from approx. £15 upwards.
It isn’t difficult to do yourself, this year I bought an iron, waxes, and edge tools plus brushes etc, downloaded instructions from Edge and Wax (free), you do need space to do it ie shed or garage as it is messy, I use a black and decker workmate as it secures the skis well, you can use a table and vice though, each layer of wax you apply you have to scape and brush off the excess, this is what makes the mess, but with a decorators sheet on the floor to catch it no problem, the outlay on equipment was about £80 but as I service 3 of our own sets of skis several times per year I think its a good investment. This way you can also choose the angle you want your edges set to.