Back in April 2011, I bought the Paul Frank Toddler / Kids Underwear from Target. They didn't last long enough. The elastics became less stretchy after sometimes. But I like them and used them all till now.
When it was time to look for some new underwear, I checked out many places and couldn't find something that suit my son. We prefer something that has shorter length from the waist to the crotch. Most of the ones we found at Target or Kohl's (made by Fruit of the Loom or Hanes) have deeper crotch to waist length.
Finally I found the underwear that fits well for my son at Carter's. And they were having 50% sales during the Labor Day's weekend. I got the Carter's Cotton 7-pack briefs at $12. Regular price is at $24 + tax. I think I score a good deal here. I bought 2 packs of the size 6-7, Carter's largest size for kids.
They have the 3-pack briefs for $12 regular price, sales price at $6. The 7-pack is a better deal. I think this is the best offer I've seen at Carter's for the underwear.