Last night, bidding had reached $6000. The auction has been viewed around 30,000 times and more than 400 people are keeping a watch on the sale.
All funds raised will go to Samoan company Event Polynesia, the main funder of the development of professional boxing in Samoa.
Samoa boxing promoter Pa'u Fereti Puni said Tuilagi was persuaded to give up his mouthguard and boots after being approached at the airport.
Mr Puni said it was a worthy cause, given there was so little funding for the development of professional boxing in the islands.
"Boxing is the poor cousin of rugby in the Pacific. The Pacific has so much talent but lacks the resources to participate in the much-needed international tournaments," he said.
"It's close to impossible to get any sponsorship in Samoa."
The auction will end this morning.
Mr Puni said he expected people would make last-minute bids, which could reach $10,000.