I have an iPhone 5 with the 2 GB + 450 minutes per month plan. I also have an iPad (3rd gen.) with LTE + WiFi. I don't have enough data usage to justify a higher tier data plan or a Share Everything plan. I can use the iPad occasionally with a 1 GB month to month plan for $20 per month. Would it be less expensive for me to have a month to month tethering plan (if available) to connect the iPad to my iPhone?