i actually just finished a pearl forum a to e project. It was my first one and a drum set that i had already. The cost is not much at all really, the biggest thing is planning out how you want to do it.
i went with the standard foam cone trigger from other plans that i found on vdrums forum. This works great and im am happy with it, but if i had to do it again i would look more into the reflection plate design.
The things that im running into with the alesis IO is that its very sensitive. I have the gain on my snare and toms basically on about 4 and im still pretty much able to peg the max velocity easily.
There are other ways around this, and hellfire has sown plans for the installation of pots that would have worked wonders for me.
if you wanna do this and you don't have a kit i would look really hard the Hellfire's X4L design.
http://www.hellfiredrums.com/archives/129 This is going to be my next build with a reflection plate style trigger that was mentioned in another thread. If you are going to spend money it would probably be much cheaper and just as effective to get some cake pans and build this than it would be to purchase a used set and then convert. im even planning on using a cymbal stand and some clamps to mount the trigger io and the toms so that i dont have to even bother with a rack because the X4L should be light enough for my pearl stands to handle them easily.
If you're like me though and already have a set that you really can't play because of neighbor (or wife/children) problems then its probably cost effective to go with the A to E conversion.
hope this helps