Wow, thanks for all the responses, guys!
I would totally spend the money if my kids were going to use them every day for extended periods of time, I know that for daily use you want something that's going to hold up. In that case, they'd definitely be worth the money.
We live in New England, so our winters are cold and snowy, but my kids don't really like being out in the snow. I get them nice jackets, and we have hats and mittens for when we're running errands, but they don't really like being out in the cold, nor do they like getting wet. So they don't really *need* snowpants except for the handful of times I'll take them out to play in the snow (which will probably last all of 20 minutes). Boots are a bit more useful, but to be honest, I can always carry them to and from the car, since it's only about 10 feet from car to front door.
I ended up going to the consignment store today and bought snow pants for $15 and $20 - they're the same brand as the $50 ones, just second-hand. The woman behind the counter was saying that they're having trouble keeping them in stock because all the local stores are completely out. They actually bring them in from a wholesaler and only make about $5 on each pair.
I also happened to get a super high-end outfit (like.. $70 retail) for the new baby for only $12, and it's in great condition.
