VistaPrint pricing model

As a VistaPrint customer, I'm very pleased with the quality of their work and turnaround time. Over the last year I've ordered postcards, greeting cards, and calendars. This is one company where the pricing is subject to change on a daily or even minute-to-minute basis.

Enclosed with my recent order was a brochure with VistaPrint's winter sales. Here is one page from that document:

What confuses me is their pricing model. For most other companies, the price per item gets cheaper as you buy more. Not with VistaPrint.

5 pens for $10 = $2.00 per pen
10 pens for $25 = $2.50 per pen
50 pens for $132.50 = $2.65 per pen

Can anybody explain this?

Another bone I have to pick with VistaPrint is their inability to handle "strange" quantities. For example, I needed to order 20 calendars. Their ordering system would let me select 10 or 25 from a drop-down list. There was no way to order 20. When I called customer service, the nice Indian gentleman helped me make a copy of my calendar project and place an order for 10 of the original project and 10 of the copied project. That was a nice workaround, but it also meant that I was charged twice for any "project upgrades." For example, even though my files were uploaded just once to their system, I was charged $2.49 twice (once for each project) for the privilege of designing and uploading my own pictures. I see VistaPrint making lots of money from these system shortcomings.