How much do you use the probe itself for probe cooking? If you don't use it all the time, then yes you could use just a remote probe for a lot less money. They won't control the smoker, but they can provide you the information, that might be better (like a ET732 which can transmit up to 300')
If the issue is why is it so much, it's because it's not a taylor or some cheap probe, but one that needs to be able to handle the smoker environment.
I know it's high, but CS sets that price based upon what they find to be the right probe for the smoker. If you think the price is high, just contact them direct and tell them of your concerns. They DO listen and if enough people tell them, maybe they make a change.
If you're looking for an alternative, I'm not sure asking in their forum for an alternative is fair (since they sell them).