I have the 3600 stick packs for $45 in my store. I also have matched race cells (to be built) in the store-3300s, 3700s and 3600s.
http://www.rc-monster.com/products.php?cat=18
The stick packs are almost always going to be spot welded with thin aluminum tabs. They work fine, but soldered batteries are better, as they have lower resistance.