Before Jio, different players held monopoly at different pockets and Jio flattened it. (Think BPL in Kerala, Airtel in metros, BSNL in rural areas, Orange in tier two cities). Because of this, when a provider increase prices, others will follow suit as everyone benefitted. So I assume the prices were high before Jio, and Jio did a correction.

Jio, will soon become a monopoly and as the article says, might jack up prices when they have the bigger slice of the pie. An acquisition of the second best then would seal the low price game and everything will go up then. Thats what Airtel was doing when they were number 1 a while back.