The 20-30 Mbps speeds are restricted to some areas. Urban areas such as Bangalore, Mumbai and Hyderabad enjoy great speeds in broadband as well but for the majority of indians, reasonably fast and cheap internet connectivity means Jio. Also, the 20-30 Mbps speeds are not the norm outside certain areas but they have been able to cover a reasonably large part of the entire country.

One carrier (Jio) has a 4G only network throughout the entire country, no 3G or 2G - benefit of coming in to the market late.

Copying this, almost all carriers are in various stages of decommissioning their 3G services and migrating to 4G countrywide. So, even in remote corners of the country, 4G is more widespread now but the speeds are not always 20-30Mbps across the country.

The prices posted by OP seem to be referring to the carrier Reliance Jio. Their network speeds were great initially(20-30mbps when other carriers we're hardly at 5-10mbps). The speeds have deteriorated significantly now. The network seems to be reeling under the load of it's huge user base.