But the former Newcastle and Cardiff striker will repay his fee with interest if his goals end up keeping Sunderland in the Premier League.
He may have scored only four goals this season, but two of them have brought 1-0 victories – including his 83rd-minute winner at Aston Villa on Saturday to give the Black Cats a four-point gap from the drop zone.
His strike came a week after being left out of the squad the week before against Chelsea.
Chopra said: "The man things is that we've got three points and we've got that little bit of breathing space now over the teams below us.
"We knew it was going to be tough when we came here and full credit to all of the lads who put a good shift in.
"We've got a lot of good players in our team and a lot of ability, it's just a shame that we're so far down the league table.
"But we know that whenever we do play well and get chances, we've got players who can put them away.
"I was very disappointed last week to get left out, but I knew the only way to get back into the team was to perform well in training. I managed to do that and my next step is to try and stay in the team and to score goals.
"A lot of people would have still been saying they paid £5m for me and I'm not worth it. All I have got to do is keep trying to score goals and shut those people up.
"Thankfully for me I managed to do that (on Saturday) and we got a massive three points."
Chopra was introduced just before the hour in place of fellow frontman Roy O'Donovan.
And he produced a calm finish after being sent clear by Kieran Richardson, exploiting hesitation by the Villa defence and their troubled keeper Scott Carson.
The Sunderland forward said: "I knew if I made a run in behind their defence there was going to be enough space.
"Kieran played a fantastic ball to me and I knew as soon as the ball had come to my feet I was going to chip it over the keeper. I was just surprised that Scott didn't come out a bit earlier to try and force me into a decision.
"To get a win means so much to the fans and the players because people have been talking about us having gone so many games away without a win."
It was a first away success at the 17th attempt – including the Carling Cup loss at Luton.
And they did it without their talisman Kenwyne Jones, who stayed at home with flu. Chopra added: "We showed that without Kenwyne we can win games. But Kenwyne is a big player for us because he gives us something different.
"The players that have come in, like Daryl Murphy, did fantastically to fill Kenwyne's shoes.
"The main thing us is that we've managed to get three points away to Aston Villa, which nobody apart from the people at Sunderland Football Club would have thought we would do.
"It just gives us that little bit of breathing space on the teams behind us.
"We know that it is all down to us now and we can only chuck it away."