I have two kids (6 and 10), I make a decent salary, and I bought an iPad.
I will openly admit that at least part of the reason that I bought it was for the kids to use. We have a lot of trips this summer - we are on one of them right now as I write this on my iPad from Bozeman, Montana - and I'm tired of the kids borrowing my iPhone and then draining the battery playing games. I could have bought an iPod Touch or something else, but I wanted an iPad for myself anyway.
Still, the iPad is mine. The kids use it as much as I do, but fundamentally it is totally understood in the family that it's "Dad's iPad". So if I want it, I get it. If I say "ok, enough Plants vs. Zombies, kids. Look out the window like we did when I was a kid" then there's no complaining (well, not much). It's a priviledge to use the iPad not a fundamental right.
If my kids wanted an iPad, I'd laugh and say "yeah, right, keep dreaming" but if they want to play with an iPad, I'll let them use it.