Any pet owner has a responsibility to keep their pets safe and within their control to a certain degree at all times. This is important whether you own a dog or a cat, but the legal responsibility and consequences are put on dog owners much moreso than cat owners, so dog owners need to take more precautions to protect their pets and themselves from the law.
The cost to install an invisible dog fence is an important factor to look at when you're deciding on what type of fencing you want to use. Chain link is definitely more expensive and privacy fencing is even moreso and both of those systems have their own problems in terms of keeping your dog in the yard. If you're going to go with invisible fencing, there are a few things you need to know. Doggy Bakery has some of those, but here is more.
The cost of installation alone can be over $500 and probably closer to $1000 depending on the size of the area you want your dog enclosed in. You can knock this cost out by doing it yourself, but it's a lot of work to do and it's not an easy job. If you're elderly or disabled, this isn't something that you can do yourself without risking injury.
Something else that you have to keep in mind is that the collars for the dogs don't work without batteries and you can expect to spend anywhere from $50 to over $100 per year in replacing the collar's batteries.