There was widespread condemnation when the prices were announced with the cheapest tickets on general sale for the May 28 final costing 150 pounds plus a 26 pounds booking fee.
Platini, who was in London for the handover of the Champions League trophy to Mayor Boris Johnson, told reporters. "It was a mistake, it was not good. But it is not easy to decide the price of the tickets in the Champions League final.
"We have received 200,000 requests for 10,000 tickets and now if you want to buy the tickets on the black market these tickets are 10 times the price that we decided.
"Perhaps in the future we have to have a new category for families that is less expensive. But if you put those on the black market how much will they cost?
"It was not a good communication and I apologise about that."
The final, returning to London for the sixth time and the first since Wembley was rebuilt, will see either Manchester United or Schalke 04 play Barcelona or Real Madrid.
United won the first of their three finals in 1968 at Wembley, while Barcelona also won their first final at the venue when they beat Sampdoria in 1992.
Platini said: "I'm sure the final will bring emotions in a true football city and a true stadium of football - Wembley."
The trophy handover ceremony, at London's Guildhall, attracted many leading figures in English football including FA chairman David Bernstein, a Manchester City fan and former director of the club.
However, Bernstein said, it would be "very special" for United to make it to the final.
He said: "We are very hopeful that Manchester United continue to progress and represent England.
"Club football in this country continues to be as strong as ever and five of the last six finals have involved an English side.
"There's no denying that Sir Alex Ferguson's side face a tough task against Schalke but to have an English team in the final at Wembley would be something special.
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