Only time I've been able to get a discount on Arc'teryx stuff is at REI during one of their season sales. Every other place seems to have restrictions on the coupons preventing you from using them on the brand. From what I understand, Arc'teryx is one of the more tightly restricted brands when it comes to pricing and sales, so you may just have to pony up and pay full price. Some sites have previous season merchandise on sale, but it's often in weird sizes and colors.
That said, I have the Cerium LT as well as an Alpha SV and think the money I spent on both was well worth it. That said, I did pick up both from REI with a coupon some time back, and probably would have been much more hesitant to pay full price for either.