{Reader Question} Why don't I purchase a lot of Mac makeup?

I was asked this question on my Formspring, and I thought I'd address it here instead because it is makeup related. First off, it's not a matter of price. Compared to other high end cosmetics brands like Chanel, YSL, Dior, etc, Mac makeup isn't that expensive. For instance, a Mac single eyeshadow is $14.50 while Estee Lauder is $20, Dior is $28, Shiseido is $25, etc. I has to do more with how I go about buying makeup. I have a fairly large collection, so if I already have a similar shade from another brand, I am not likely to purchase one from Mac that comes out from a new collection. I look for uniqueness in a product. Another thing is that Mac isn't sold at Sephora. I get a lot of gift cards to Sephora and am therefore more likely to shop there instead of spending my own money (not that I don't spend A LOT of my money on makeup else where). And finally, I feel like Mac releases too many collections. I mean, they have something around 20 collections each year. That's crazy! Most high end brands have four or five at the most! I feel like Mac tries to get me to buy makeup just because it's limited edition. Proof: Stereo Rose. It was sold out every where weeks before the collection even launched! That's insane! It's not like I'm never going to find a similar shade. I just feel that it is excessive sometimes. Combined with reasons number one and two, it's not entirely unreasonable that I don't purchase a lot of Mac makeup. It has nothing to do with pricing or just being against the brand. I just spend my money a bit more deliberately. What about you? How do you feel about the number of collections that Mac releases every year? What about they're pricing? Let me know in comments!