On December 5, US private equity player Hellman & Friedman but in a rival $6.45 a share bid, valuing Trade Me at $2.56b.
Craigs Investment Partners deputy head of institutional research Stephen Ridgewell described Hellman's $6.45 bid as a "tepid" increase on Apax's offer.
"The scope for further significant re-raises by private equity bidders may be limited, with the best scope for a significantly increased offer being from a potential trade buyer," he said.
China's Alibaba, which has entered other markets by buying an incumbent, is seen as a potential trade bidder.
On August 22, Trade Me said it was distributing $100m via a 22 cents per share special dividend, as the online auction company announced it turned over more than $250m for the first time to deliver a 3.9 per cent increase in net profit for the year to June 30 of $96.6m.
The company was founded by Sam Morgan in 1999.
Morgan sold it to Fairfax in 2006 for $700m. The Australian publisher, in turn, floated Trade Me in late 2011 at a $1.07b valuation.
MacDonald is one of only two people to serve as Trade Me chief executive - the other being Morgan.
Trade Me shares opened at $6.17 this morning, down 0.3 per cent.
Speculation of a trade buyer entering the fray has been balanced by conjecture that Hellman and Apax could merge their bid rather than ramp up their (so far very modest) bidding war.