You can do better than this. I am always in a wifi area so I don't need much data. T-mobile will give 200 MB a month for free to a tablet.
I am consistently using 120 MB a month or so and get free cell coverage for my tablet. Using google hangouts (somewhat flaky) I have been able to drop my cell phone entirely.
I bought a new iPad mini and figure that after 2 years, my device will be paid for with cost savings (my old phone plan was 25 a month) and I am entirely in the black