I always used to do the same until a couple of years ago. But with their age gaps the cost of their presents vary so much, and I'd end up just buying things for the sake of the numbers. I try to keep it roughly the same so it isn't noticeable, but this year I told them it would be quite a bit different because Jimi and Zac both wanted something expensive where as all of the others presents combined didn't come to the same price.