And yet, Mr. Agarwal complains that the Best Price store has also effectively become a competitor. That is because anybody with a valid business registration can buy from it, and the store has 50,000 member-customers. As a result, in addition to buying supplies for their businesses, many people end up doing their household shopping there, too.

Loading a large consignment of supplies at Best Price one day last week, Mr. Agarwal complained, “This is not a wholesale store.” Instead of being able to buy single items, as at a retail store, he said they should be required to buy wholesale quantities. “They should have to buy six or 12,” he said.

Sumit Gupta, the Best Price store’s manager, said there was little he could do to prevent its members from buying whatever they wanted, as long as they could show that they were registered business owners. The company stocks individual packets of many things, he said, because small retailers demand the option to buy in small quantities.

For now, Mr. Agarwal straddles two commercial worlds.

The morning after stocking up at Best Price, his own shop, Kwality Super Store, was buzzing with customers. Mr. Agarwal and his father, Anil, stood behind the counter. As in most Indian stores, there was no cash register. Mr. Agarwal asked customers to call out the items they were buying, and he hand-tallied the totals on small slips of paper.

One customer, Bhupinder Singh, bought tea, soap, lentils and other supplies. He said he frequented Mr. Agarwal’s shop — but also the Easy Day retail outlet that Bharti has opened down the street.

Easy Day often has prices of up to 10 percent less on packaged goods like biscuits. But he sells the milk from his dairy to the Agarwals, and the family offers him credit on his groceries or offsets his purchases against what it owes him for milk.

Which store he visits, he said, “depends on how I feel that day.”