I worked in the wireless industry- my last wireless experience was network design. The engineers make good money, but usually not more than the 60 to 80K. If they are straight contractors, they might make somewhat more, but have absolutely no benefits. Medical, dental, and assorted benefits add up. I didn't know any engineers with a 400K house AND a stay-at-home spouse and kids. Not even close. I'm in Seattle and the cost of living is a little bit lower but not much. It's strange that their house in TX was for sale for just over 100K and then they moved up to over 400K.
They had some sort of newish SUV in their driveway; don't remember what kind. I agree that there is something slightly fishy about the finances.