I agree with "you get what you pay for", to a point. It IS possible to pay a lot less if you have the time, knowledge, and energy to properly set up the sytem and train your dog yourself. We bought the Petsafe system for our dogs. We paid about $250 for the system and bought extra wire to encompass most of our 1 1/2 acre yard. We ran the wire ourselves and my husband hooked up the transmitter. Being a stay-at-home mom at the time, it fell on me to train Moe and, later on, Tally. We also had to buy another reciever when we got Tally (she and Moe each have been through two recievers). You don't just install the system and turn your dog loose... it takes MONTHS to reliably train a dog to an invisible fence system. If you don't have the time, then it's worthwhile to get the much more expensive "Invisible Fence", which is installed for you and then they train your dog(s). You just pay the bill.
Keep in mind that there are drawbacks. It may keep your dog in but doesn't keep people or animals out. If you live near a busy road it is not worth the risk. Moe has gotten out several times... several times due to weak or dead reciever batteries and once due a wire break (we disconnected the fence till we could find and fix the break). A couple times he got out because whoever was home neglected to put his collar on. It is possible to have breaks in the wire that can be difficult to find (ours has been broken by a backhoe and, on MANY occasions, I broke the wire while digging in my garden (it goes through three of my gardens). It also goes under both driveways... we buried PVC conduit before paving so we could run the wire underneath. Once, the spliced connection corroded when it got exposed to water and we had to redo the conection and replace the little thingy that covers it. We buried our wire where it ran over grassy areas using an edger but in the woods the wire is above ground but covered with leaves. Over the years plant matter has built up so that the wire is hard to find. If you get invisible fence invest in a wire-break detection thingy-ma-whatzis (it's my husband's job to find and repair breaks B) ). Also, close lightning strikes can affect the fence. It fried our transmitter once, causing us to replace it. And put it out of commision temporarily a few days ago. Fortunately, with a little fiddling we got it working again.
Continue to look into it and see if it will work for you and your dog before making the investment. I'd stay away from anything that costs $56... either it is junk or it is not what you think it is.