This is probably a losing effort, but to be clear:
MS asked us to make some DLC. We chose to do that. We made a proposal back to them with what the DLC contents would be. After some back and forth, they agreed. They set the price. They alone control this. HW is a MS franchise and they have guidelines for how much stuff costs. That said, yes, we knew what the price would be.
Personally, I think the price is fair. It's clear that you guys do not (overall). We can disagree on that, particularly since no one is forcing you to buy it:) It's worth pointing out that map packs are easy to figure out. They're easy to make. They're especially easy to price. Game modes for a strategy game on the console are less clear-cut. We knew there would be some consternation over the modes coming out as the first pack, but we thought it was something that would be very popular. Time will tell. If there was a mistake made with the pricing, then I'm confident that will bubble up in the pricing analysis.
Overall, the based on what folks are playing right now, I'd say a) the DLC is popular and b) the DLC is doing its "job" in refreshing the feel/community for the game. Someone made the comparison to Horse Armor. That's an ironic comparison given that, to date, the Horse Armor remains in the top 5 or top 10 "most purchased DLC items" (at least based on the last numbers I saw).
Anyhow, we (and MS, I imagine) have clearly got the feedback on the pricing.
Lead Designer, Halo Wars