On Tuesday, the Evening Times revealed a seven-strong team from SPT ran up the bill while visiting companies bidding for huge contracts for the upgrade of the underground network.
Senior members of the SNP have questioned the cost and whether it was necessary for so many people to be involved.
But Jim Coleman, chairman of the transport body, has defended the decision to visit firms in countries such as Spain, Switzerland and Canada.
He said: "It will be a completely new metro system and the idea that somehow you can do that without actually going to see the companies and taking the appropriate staff is inconceivable.
"If it was a private sector contract on that scale, nobody would bat an eyelid.
"We need that detailed information before we take a decision which will affect the Subway for the next 30 to 40 years.
"Was it necessary to spend £38,000 on accommodation and travel. Yet it was."
Anne Folin, who has been appointed as a member of the SPT board, said: "The seven who went were staff - they were technical officers.
"There is no question it was a jolly or some sort if freebie."
Charlie Hoskins, director of projects, said visiting the firms bidding for the work would result in substantial savings.
He added: "We are talking millions of pounds over a 30- year period."
Work is well under way and on time for the Subway's £288million upgrade, which will result in state-of-the-art driverless trains.
It will also include new signalling and platform screen doors.