"The comment was made, 'I wonder what will happen if you put it up on Trade Me with a $20 reserve and a $150 buy now'," he said.
"I didn't think it was going to go this mental."
If anything, he thought he'd lose money in the auction.
But bids on the "unwanted Christmas gift", hit $5150 early this morning, before Trade Me cracked down on the larger bids.
There have been a total of 93 bids, 2537 have added it to their watch-list and the page has had 142,283 views.
Bidding closes on Saturday at 4.57pm.
Mr Shefford engaged with 205 people on the site who had asked questions about the auction.
One person asked if he would consider selling for $80, to which he replied: "Yeah, sweet as, it will be 20 bucks post and packaging."
The thread of conversation showed an attempt by the seller to bring one of the top bidders, Jackson93 out of the game, by removing his initial bid.
When questioned, Mr Shefford said: "this is a fair auction, I have something for sale. The winning bidder will own it. All unrealistic [bids] have been removed."
Jackson93 put in his final bid of $5100 at 11:12pm yesterday, which was then superseded this morning by poppaelf with a bid of $5150.
Unwanted Christmas gifts have flooded Trade Me over the past few days.
Among the slew of socks, bevy of books and crates of cricket gear were one-of-a-kind auctions.
The more unusual included a generic KiwiRail Christmas card, touted as "unique" and "personal".
A stormtrooper cookie jar and a batter dispenser, were also under the online hammer, as was a Star Wars lightsaber thumb wrestling book and a Minecraft cardboard head.
Trade Me spokesman Logan Mudge said on Boxing Day: "We're expecting to see thousands of unwanted gifts change hands in the next few days, and bargain hunters and opportunistic sellers will be out in force," he said.
"Trade Me has an important part to play in extending the lives of those items, getting them out of Kiwis' wardrobes and rubbish bins, and into the hands of people who will use them and appreciate them more."
More than 166,000 searches were made on the site on Boxing Day last year for unwanted gifts. The most popular categories included outdoor furniture, baby gear, DVDs and camping equipment.
"If you unwrapped a sun lounger, bassinet, copy of Star Wars Episode IV or a tent that you don't want, we think you've got a good chance of it being snapped up by a Boxing Day buyer onsite," Mr Mudge said.
In the past, women's clothing items have been popular re-sale items on the site. Mr Mudge expected that trend to continue.
"Our women's clothing category had thousands of listings that started on Christmas Day and Boxing Day last year. Buying clothes for others is a high-risk business and our 2014 data shows some of the most spectacular present fails were in the dress, shoe and lingerie sections."
Trade Me's picks for popular unwanted gifts this year:
1): Adele CDs
2): Selfie sticks
3): Socks
4): Lingerie