Here's a tip: YMAA Publication Center has monthly email offers. One of which allows you to purchase product sets at big discounts. All you need to do is Opt-In to their email list
http://www.ymaa.com/signup
New Products - announces new products that are available.
Specials - announces products and / or sets that are on sale for 30 days. (usually, they send a reminder at 15 days to go). You will need to use the 'coupon code' to make the discount show in the order form.
Authors on tour - They don't seem to use this feature as much as I would like.
Oh, yea.... YMAA doesn't trade, sell or abuse your email address.