Why is it so insanely overpriced to upgrade from Adobe CS4 Design Premium to Adobe CS4 Master Collection?

Here's the info:
Adobe Creative Suite 4 Design Premium, Design Standard, Web Premium, Web Standard, or Production Premium: upgrade to Adobe Creative Suite 4 Master Collection is 1,599 USD.

Here's the craziness:
Adobe CS4 Design Premium costs 1,799 USD for the Full Retail Version
Adobe CS4 Master Collection costs 2,499 USD for the Full Retail Version

that's a difference of 700 USD; however, it costs 1,599 USD to upgrade?

am I missing something? and why would Adobe CS4 Web Standard, costing 999 USD, cost the same to upgrade as Design Premium?

As far as I can tell - if you give Adobe more money, then you get a worse deal.

Seriously - can an employee from Adobe explain this insanity? Why wouldn't the upgrade be the difference in cost? And finally, who came up with this pricing plan?