I dropped Howry last week, but a couple of days later, I decided I wanted him back. So, I tried to put in a waiver claim, but received an error message from Yahoo saying that I had to wait to get the player until after he CLEARED waivers. I'm assuming this is the same for all leagues.
So, to answer your question: If you're trying to pick up a player off of waivers that you dropped, you can't use a waiver claim no matter what your priority is (10 or 1). You must wait until the player completely clears waivers (in my league, this setting was set for 3 days).
Hope that helps.