The Royals have already made three moves in the current transfer window, bringing in Hope Akpan from Crawley, Fulham's Stephen Kelly and Daniel Carrico from Sporting Lisbon.
Akpan and Kelly both made their debuts in Saturday's 2-1 win at Newcastle and McDermott was impressed by their contributions, insisting Reading do not have to spend big to get results.
"People sometimes question our transfer policy - but we do what we have to do and work with the players that we've got," he told the club's official website.
"I brought Hope Akpan on and I thought he was fabulous. We spent 300 grand on him and you could see the qualities he's going to bring to us. He's 21 years of age and hungry.
"We paid 300 grand for Adam Le Fondre, and you couldn't buy his right sock for that now. We bring in the likes of Stephen Kelly, Daniel Carrico - they don't have to cost five or six million."
On the prospect of making further additions to his squad before the transfer window closes, McDermott added: "We'll do what we do. If there's something that comes up for us and it's right and proper, and the owner decides he wants to do that then we'll have a look at it."
Reading are currently a point adrift of Premier League safety in 18th place after securing back-to-back wins.
McDermott believes the fact that some of their fellow strugglers are clubs that have splashed the cash in recent transfer windows proves spending does not necessarily equal success.
He said: "Don't get me wrong, if I get given a load of money to spend then I'll spend it. But in any case throwing money at things doesn't guarantee success - there are plenty of examples of that.
"There are teams in this league who have signed players for a lot more money than us and it's not necessarily helped."