Everton boss Roberto Martinez has defended Romelu Lukaku over his recent form slump.

Martinez believes Lukaku was a "cheap" signing at £28m from Chelsea and will prove better value for money than Wilfried Bony's move to Manchester City.

"The market sets the value," said Martinez. "If you said Bony went to Man City for the same money and how old is he?

"I am looking at Rom and what he done for us from day one is taken responsibility. He is a '10'. He comes in, wants to help the team and is always available. You couldn't get a better, safer investment than him as a young man.

"The world is at his feet really. I don't see it as a poor investment or expensive investment. He has scored more goals than last season at this stage [10 compared to nine] and the second half of the season will be his best.

"He has become a better player than last season there are no two ways about it. The time to assess is at the end of the season, but he has been a cheap signing for us what he is."