Redknapp's side had to be content with just a point against Norwich in a goalless draw at Loftus Road.
Despite extending their unbeaten Premier League run to five matches, the Hoops are six points of safety as a missed second-half penalty by Adel Taarabt proved costly.
Redknapp handed debuts to £12.5million centre-half Christopher Samba and on-loan Tottenham midfielder Andros Townsend, while Jermaine Jenas came off the bench.
With £8million striker Loic Remy set for a spell on the sidelines after suffering a groin injury in training on Friday, such a hefty outlay during the January transfer window could prove money laid without reward should QPR fail to climb out of the bottom three.
Redknapp, however, insists no matter what happens over the next four months, all players brought in were sound investments.
"Everyone is going on about Samba. You will sell Samba at the end of the season if you want to sell him because Samba should be playing for a top-four team," Redknapp said.
"He is a monster of a player, as quick as lightning, fantastic in the air, can play. He has got the lot and is the full ticket.
"At the end of the season, if it doesn't go well, they will go and get £12million for Samba, not a danger.
"There will be managers out there who will be thinking 'I thought he was gone, but now he is back in England'.
"There will be takers for Samba all day. So they have not done their money on Samba.
"Remy for £8million, if he can come and score a few goals, he will be £12million. We (Tottenham) tried to buy him for £18million last year.
"The two kids from Tottenham. One was three grand (a week) and the one doesn't come to a lot of money.
"I have not brought players in here who were s***, that we can't give them away. They are good players.
"The club's invested, but they will get their money back on those players."
Redknapp maintains there is not much more he can do as the former Tottenham boss looks to plot a safe passage towards Premier League survival and next season's bumper £75million TV deal.
"I am getting everything I can out of the players who are here. I can't do anything more than that," he said.
"You look at the games we have had since the turn of the year and you would have taken the points we have got.
"However, against Norwich was the game when we thought we really had to try to get three and if we had scored penalty, then we win the game."
QPR travel to Swansea next weekend, and then host leaders Manchester United before a date with fellow strugglers Southampton at Loftus Road at the start of March, a month they also tackle Aston Villa.
Captain Clint Hill has called on the team to rise to the challenges ahead.
"The next period is key. The end of February and March is a massive time for this club," he said.
"We are playing teams in and around us and those results will determine where we are next season."
Hill added: "Obviously with January (spending) as well, everyone has put the spotlight on us. We have to ignore it.
"We need to concentrate on our results as if we look at other teams we will be bogged down by it.
"We need to keep the unbeaten run going, but need more wins than draws."