We have those wireless handsets in our shop. You were told correctly, they are way overpriced and are junk.
If the two shop foremen get their handsets to last more than three months before they shit the bed, it's considered a good quarter.
You are correct, the backbone of the system with the desk phones works great, but those wireless phones are a joke.
Unless you can get some sort of maintenance contract that offers free replacement when they break, I wouldn't go that route.