You can save $6 bucks if you already own it for another platform:
Single User License Additions
If you currently own a single user license for at least one product, you can purchase a single user license for another product for yourself at a discount. This includes the case where you are switching from one platform to another.
Note: This discount does not apply if you currently only hold a license for iSilo™ for iPhone, as that product is already offered at a significant discount and sold through Apple's App Store. The discount also does not apply for purchasing iSilo™ for iPhone for the same reasons.
You will need the registration code for the single user license that you currently own in order to purchase a single user license addition. You can find the registration code in one of the email messages you received after purchasing your current license. If you have misplaced your registration code, click Lost Registration Code Request.
Choose the product, enter the quantity of single user license additions you want to purchase, enter the registration code for the single user license product you currently own, then click the Add to Basket button.
The small problem with this is I had to buy it through isilo and not the market.
Then I had to sideload it. The downside is it doesn't show up as one of my 'Installed' apps when I browse the market.
No big deal, i guess.
It just means whenever an update is released I will have to again sideload the app.
So, if your device allows sideloading, you can save $6 on isilo if you have/had it on another platform.