Well, I personally hate these tiered events - get rid of them.
Lets just be honest here. The items in these tiered events are being specifically sold as a product. Instead of attaching a price tag to these items, they are grouped into spending gimmicks called tiers.
It is these items in these different tiers are what people want, and they are willing to buy these tiers.
When you get to the upper levels, the items in the item mall, for the most part, are of no use to people except for the OPs. Most people are not buying OPs to use them for their original purpose. It is just a way to exchange one currency to another $$ to AP to OP.
Aeria should be selling all of these items that they offer in these tiered events directly in the Item Mall.
Then when Aeria want's to "encourage" people to spend more, then start having BOGOs or similar events.