Batman:

 

When the iphone 4 was sold, it was half price at vodafone if you signed up for a $29 plan for 2 years, and it came with 3GB data! (about 2.9GB more than normal plans at that time)

 

 

I did that on my 4S, not that plan, but a plan. Cancelled the plan days later, got billed for ETF, and basically got the phone now for an extra $20 spent, rather than wait for outright. That door since closed.