I think Costco cannot be beat for yumminess and price.
i like Sprinkles in Beverly Hills (plus more locations) for cupcakes...
i've never had a costco cake, actually.
They're amazingly cheap - less than $30 for a half-sheet. They're very moist and don't have too much cream. The fruit, if you get a fruit one, is very fresh.
costco makes great pie.... every thanksgiving i am forced to make the decision whether i should bake pumpkin pies or buy ones that are 10xs the size for half the cost of the ingredients.
I love Sweet Lady Jane's on Melrose in LA. And if anyone's keeping track, my half birthday is coming up and their frog cake looks delicious!
I love Beckers Bakery in Manhattan Beach, CA. All cakes are topped with butter cream frosting--no exceptions--and the cakes and cookies are delish. You can also stroll across the street to Cupcake Couture MB for the most incredible cupcakes. So yummy. (Beckers has great sandwiches too, but I guess that would be for a different group...)