Right now in my secondary number Jio, I have earlier (2.5 years back) paid just Rs349 (Rs399 - Rs50 voucher) with benefits UL calls + 100SMS/day + 1.5GB/day for 84 days. It will be Rs719 for the same benefits from 26th Nov. So I am already enjoying the same benefits by paying just 48% --> 52% benefits in my case.
No investment (without a risk) like FD gives 8% interest now. So calculating with at least 8% interest per year is wrong, imho. 5-6% is fair enough. Also returns from investment (again without risk) is always smaller than inflation as well. So the loss of interest value is more than compensated by inflation already. For example, the amount I saved today by not doing advanced recharges this year, will not buy me the same amount of goods / service by next year.
So guys with BB in home / office, it is better to go for Rs1498 in Airtel / Rs1299 in Jio. There are data top-ups with base plan's validity for emergency heavy usage, in both Airtel as well as Jio.