charger beyond free data download are substantially low
Not *that* low. It's still too much - much more than we'd charge per MB (well... hard to charge per MB when per GB it's under Rs20).
It appears that the pricing is staggered, so once you got to 100GB you'd end up owing over 7000 rupees:
((((3*20)*1024)+((5*15)*1024)+((5*12.5)*1024)+((10*10)*1024)+((10*8)*1024)+((10*6)*1024)+((50*4)*1024))/100)=6528+850 plan price.
The alternative structure (which would be preferable but I don't think is very likely) still leaves you owing over 4500 rupees: (((93*4)*1024)/100)=3809+850 plan price.
Frankly, you'd be better off with Airtel's 200GB @ 30mbit/s plan for 7999, unless you can show us that the latter option is actually the case. But as mentioned, this is VERY unlikely because for those downloading 101GB, they'd only owe 2406+850 which is quite significantly less than what someone downloading only 100GB would owe - not to mention it would destroy their 4mbit/s unlimited pricing.