The price difference may be explained by different prices at the manufacturer due to different market power - supermarkets have forced the prices they pay down everywhere by being 'bigger than the manufacturer'.
But it may also be Reliance cross subsidizing from its retail business - selling at a loss in order to force rivals out of the market.
That would be an amazing play because they can destroy the existing distribution channel, then replace the small shops at the end of it in a few years by rolling out their own small stores with very low prices and while increasing the wholesale price they now control so the family owned small stores can't compete.
This is a big 'problem' in the west too, where venture funded 'startups' can often out compete small scale traditional rivals in price temporarily by providing goods to the market at much less than cost, burning investor money until the rival way of doing things is broken, then jack the prices back up and reap the profits as a local monopoly.
I say problem because I'm not sure if in the end it is good or bad. Bigger market players have options to destroy smaller players is a tale as old as time. Local monopolies are bad though, and I think government needs to take a stronger role in regulating these like they would a larger scale monopoly.