The difference in price is more of a fundamental difference in function between the machines.
The Selmi, as a continuous tempering machine, will keep the chocolate in temper throughout the working day without needing to slowly raise your working temperatures during the day. This is achieved with a closed refrigeration/heating loop that as the name suggests, continuously de-tempers and re-tempers the chocolate.
The JKVs are wheel machines, normally with light bulbs as a heat source and forced air for cooling. They use seed chocolate for tempering, and as such will need some attention through the day. The chocolate will thicken and you will need to gradually raise your temps until it's no longer in proper temper. Then it's time to stop and re-temper.
So, you're paying that extra money for extra throughput and added convenience. On the other hand, if you're a DIY type, these machines (Selmi) are much more difficult to fix yourself.
I personally like Linda use Hilliard's machines and they are certainly up to the task. They are rugged and simple to operate and maintain (they use light bulbs/forced air too). I was lucky enough to find all my gear used for an unbeatable price. For me it was an easy choice because of the DIY aspect, since I do most of the maintenance/repair work myself.