The five-time Champions League winner left Tottenham to join Real Madrid in 2013 for a fee of £85.3 million in what was an extremely successful move for the Welshman.
He made the move at the end of the 2012/13 season after netting 26 goals in 44 games for Spurs and was wanted by a number of top sides, including United.
Speaking on the Stick to Football podcast, the 36-year-old admitted that the Red Devils offered him more per week but he was set on joining the Spanish giants.
"I spoke with David Moyes, but my heart was set on Madrid anyway
"And I had something in place with Daniel Levy, more of a gentleman's agreement just to be like ... Because he didn't want to sell me to a rival also ... 'We don't want to strengthen another team'.
"So if a team did come in from Spain, Italy, wherever, Germany, wherever it may be that, I could potentially go because if we didn't qualify for Champions League, which we didn't, I was then able to go there. So we had that gentleman's agreement even though he made it very tough.
"I think I chose the right one (based on the) last 12 years," he added.
"I didn't go down the wages route with United. I didn't get that far. They offered more money to buy me, and a player (too), but it didn't really get any legs to be honest, no."
United's only addition was the £27 million signing of Marouane Fellaini from Everton on the final day of the window, a player who never lived up to expectations.