The 41-year-old, who became the world's most expensive player when he moved to the Santiago Bernabeu from Juventus in 2001, said that time will tell whether the Welshman is worth his astronomical price tag.
"You need to ask [if he is worth the price] in a year's time," he told Canal Football Club.
"Ten years ago, they bought me for €75m (£48m at the time) and I said I wasn't worth it. Today, I tend to say a player is not worth that.
"Two clubs agree on a price and no-one is forcing the other to do anything. That's football. Unfortunately, it's incomprehensible with what's happening today to pay so much."
The previous world transfer record was £80m, set when Real purchased Cristiano Ronaldo from Manchester United in 2009.