Very good points in this post, but it seems to me that they are only valid if you look at a single line of products / services at a time. When you put multiple

Very good points in this post, but it seems to me that they are only valid if you look at a single line of products / services at a time. When you put multiple products/services in one store, that is when your products get to be next to both competing and non-competing (non directly substituable) products, there are other consumer feelings to add like the sum of all things they're going to buy -- whether or not they have a budget, the sum of the things will either look "cheap" or "expensive". And who knows what they will buy next... if they come back at all.