Elantris Hardcovers coming + Question

I just got in an order of ELANTRIS hardcovers, which I'll probably start selling signed and personalized through the website next week.  These cost me more than the MISTBORN ones, since it's been too long and I couldn't get them through Tor any more, but they aren't remainders and look pretty nice for books that have been shipped back and forth between bookstores for three years.

Keep an eye out for them.  At how much they cost, I'm not sure how much of a discount I'll be able to give them, but I'll at least knock a couple of bucks off for the first month like I did with Mistborn. 

In line with that, I've got a question for you all.  I want to offer signed bookplates (stickers you can stick in books you've already bought).  I figure that if you've already bought one of my books, you shouldn't have to order a brand new one to get a signature in it.  This offers me some problems, though. 

First off, I now have a large stock of books sitting in my garage, and I'd hate to have everyone end up getting bookplates instead leaving me with a ton of money I'll never recoup.  Secondly, I don't want to make the bookplates so cheap that I get orders for thousands of them, which I think I just might if I charged only the cost of a stamp (which was my first inclination.)  Thirdly, even signing a couple hundred bookplates a month would be time consuming enough that it would eat a little into my writing time.  All of that says that I should charge something to pay for the time it takes to personalize them and the cost of paying my assistant package, address, and send them. 

On the other hand, I feel like a total cad charging money for a little slip of paper with my signature on it. 

Therefore, I put the question to you.  What would be fair, in your minds, for something like this?  I've put some options below, but feel free to offer your own.  As always, you can post on my forums, my LJ (where you can post without an account), or you can just email me.  I read all comments and posts, even if I don't always have time to respond to them.

My thoughts:
$3 for one bookplate, signed and personalized however you want, shipping included.
$6 for up to four bookplates, signed and personalized, shipping included.
$3 for up to four bookplates, signed but NOT personalized, shipping included. 

What do you think?  Too much?  Too little?  Other suggestions?