The DeWalt battery pack features two DCB204 20V MAX XR Li-Ion 4Ah batteries which are currently DeWalt's highest capacity/most advanced batteries. I ordered the pack earlier today and used my $5 Amazon 1Button App credit from this thread to bring the total down to $92.99--YMMV.
Alternatively, FactoryAuthorizedOutlet (in Cali) also has the DeWALT DCB204-2 for the same price (after $20.00 Dewalt Father's Day promotion) with free shipping.
A similar deal for a 2-pack of Ryobi P108 4Ah Li-Ion batteries for pretty much the same price made it to the frontpage in the middle of April. Thought at that time that the Ryobi 4Ah batteries could not be beat as far as price was concerned. Well, I will return the Ryobi pack that I bought then in favor of the DCB204-2.