The leasing deal is only available for 10 or more devices at a time. Google can't be doing with the admin overhead of huge numbers of small fry $30 dollars a month agreements with poor students where there is a risk they will default and disappear with the hardware. They offer this deal to institutions who will order in large numbers and be reliable customers, keeping admin costs down.
If you just want one chromebook, find the cash (maybe get a loan) and go to Amazon/best buy/pc world. Alternatively, you could wait until the mobile telcos start offering them on mobile web contracts for a monthly fee. Such deals will probably become available before the end of the year.