Real Madrid paid United a world record fee to sign the Portugal winger but Keane said the money involved to take the 24-year-old to Spain is justified.

"I'm OK with it," stated the Ipswich Town manager. "It's just the way it is.

"Clubs are prepared to pay that, people talk about Ronaldo going for £80m - I look at other players and think Ronaldo's cheap for £80m."

Keane, whose Ipswich side are in Ireland on a pre-season tour, added: "He's the best player in the world. Footballers are classed as entertainers and if you look at any industry the top people get the top money."

Ronaldo's switch to La Liga ended a long pursuit by Real for the world footballer of the year.

He was strongly linked with a move to the Spanish capital last summer but after a long, drawn-out saga in which United manager Sir Alex Ferguson said he "would not sell that mob a virus", Ronaldo insisted he was happy in Manchester.

However, the player continued to send out mixed messages about his future throughout the season and returning Madrid president Florentino Perez, who led the club from 2000 to 2006 during their famous galacticos era, said he would do "everything possible" to sign Ronaldo.

His capture came after Real had already secured the services of Brazilian playmaker Kaka from AC Milan for a reported £56m.

Ronaldo is expected to make his Madrid debut in Ireland on Monday night against Shamrock Rovers, with 11,000 tickets sold for the friendly encounter.

He is in the squad along with fellow new signing Karim Benzema, although Kaka will not be involved.

Ruud van Nistelrooy, Gabriel Heinze, Wesley Sneijder and Arjen Robben could also feature in the match at Dublin's Tallaght Stadium.

the first thin i ever wore was manu top as soon as i was born

The earlier declarations of Manchester United chief executive David Gill, which suggested that the club may still make further acquisitions this summer, rendering Sir Alex Ferguson's "no more signings" stance void, could be true as the agent of promising Brazilian starlet Douglas Costa has explained that his client is still on the Old Trafford outfit's radar.

Cesar Bottega is reported to have recently told the South American press, "There has been more contact [with Ferguson], even to know why [Douglas] isn't currently playing.

"Ferguson has studied him closely. But it is clear he wants to confirm what people have told him up close."

Costa currently represents Gremio. The highly-heralded attack-minded midfielder has attracted covetous glances from European scouts due to his strong strike-rate for a teenager, together with his growing accumulation of club honours in the Brazilian league.

Should Sir Alex swoop for Costa, the 18-year-old will join a growing list of Brazil-born players already at the Theatre of Dreams, where Rafael da Silva, Fabio da Silva and Rodrigo Possebon are all deemed to be promising prospects.

Ferguson has repeatedly tried to bring Douglas to Manchester on trial, but Gremio claim the player is too good to be considered a trialist.