Lukaku has certain attributes which make him a 15-20 million player. He scores a good tally of goals, strength and can run at defenders. Perfect for the PL really.
He has other weaknesses which mean he's not in the 20million+ bracket of stickers. Poor control, no vision, loses the ball often. You don't develop vision or control with age.
From a Chelsea point of view, they can't afford, at CL level to have a guy like this. This is why they don't want him. Which is is fair enough.
He's a top end PL striker but he's never going to be worth 30 odd million to the top European sides who have that kind of money. This idea that strikers get better with age is a bit of a myth. They tend to get worse. It's a dangerous idea to value him based on some future projection.
I'd definitely take him, with his flaws for 15-20m though.
Diego Costa and Drogba both improved dramatically from the age of 24 onwards from pretty average to world class strikers, their numerous other cases of strikers whose best form was from the age of 24-30 as well, the strikers who are prodigious at a young 19/20/21 age and who then tail off are far less in occurrence mate
I'd also question your statement about his weaknesses that cannot be developed, poor control - his control has gotten worse this season as he has looked fatigue - the same control was much better early season when he looked fresh, it also seems to be better atm when he's out wide without so much pressure on him, maybe a case of mentally needing to toughen up a bit about being played tighter - both the fatigue factor and the experience of being played tighter can be worked on with experience playing the role, sometimes he exhibits very good technique - which would tend to suggest its not about a technical inability more a lack of composure or feeling the pressure whilst being more fatigued
No vision - he actually leads the rest of the team in assists this season, would suggest differently, some of the passes he does are actually the complete opposite - 2 examples from the city game where he swung out 40 yard cross-field balls to the left etc, does he often choose the wrong option - yup same as a lot of our lads do - it's more a case of trying to do too much himself rather than a lack of seeing what is around though, being ball greedy more like a lot of younger players suffer from - including players like Ronaldo at the same age, making the better choices will come often with experience and trust in those around him
Loses the ball often - yup no argument their - but same as the above point - it's down to inexperience and trying to do the harde4r thing too often rather than the simpler more effective choice - down to experience and a bit of greediness or overconfidence again - both things that can be worked at with experience and a bit of maturity
Theirs a reason that Chelsea are being linked with forwards around 26/27 years old atm, because those things you say are not workable on in fact are a lot of the times a by product of a young player, and the likes of Cavani and Costa have learned when to do the simple and when to try go it alone, their control has improved as they've learned to slow the game down in their own head rather than it rushing full speed at them like at times it does with Lukaku, mate seriously if all he had was strength and pace then i wouldn't want us anywhere near him, its because the other areas of his game are their already - they are just raw and more erratic and that will be something he can develop. At a team like Chelsea they have no patience and want the instant product right now, hell look at Matic for an example of their lack of patience in developing a players game, it is easier to sell him on and then simply buy back once the player has had those areas of his game improved by a team with more patience