At the supermarket the items are there in front of you and you don't have to go create an account at the front desk before you can buy anything.
So you agree its the process that's the problem, not the variety of options (the tiered pricing)?
Partly. The process is clumsy, which makes it worse. However I am a great fan of usability. Don't Make Me Think by Steve Krug (see http://www.sensible.com/). If I have to stop and work out what the offer is, or even how many options there are, or how they differ, then it's poorly presented.
Some people will give up.
There should not be options unless it is crystal clear to the user why they are there and what they entail.
And it is not, currently.
It's too hard to understand the offer, it's value, the differences... AND it is too hard to purchase if you do work it out.