Keeping your dog in your yard can be difficult, especially if you have one of those “Houdini” type dogs that will figure out how to escape from just about anything. From little dogs that manage to squeeze through the smallest of spaces to dogs that can climb over any and everything, there aren't a whole lot of solutions that you can implement that are going to be cheap.
Fortunately, invisible dog fencing isn't any more expensive than traditional types of fencing, such as chain link, privacy fencing, and in most cases, can actually be much cheaper depending on the amount of area that you need to cover with it. You can learn more on this here: http://www.doggybakery.org/cost-invisible-dog-fencing/
The average cost of an invisible dog fence depends on whether you're going to install it yourself or not. If you're going to have it professionally installed, it's going to add a pretty penny to the price tag. This can be anywhere from $500 to over $1000 on top of the cost of the materials, collars, batteries, and voltage meter(s).
Something else that you have to take into account when purchasing your invisible dog fence kit is the quality of the wire that your kit comes with. Some is definitely better than others and if you don't get a quality wire that's well insulated, you'll end up having to dig it up and replace it. This can be a real pain, so it's best to buy high quality wiring to start with.