Here is a short list of forwards transferred during the current window into EPL clubs. I've included Tevez' exit here as reference. I may be missing some important signings, and maybe have some numbers wrong, but nevertheless... Maybe you can suggest the money is better spent elsewhere, but I can hardly imagine that Kone is overpriced.
Player Age Price
Alvaro Negredo 27 £22,000,000.00
Stevan Jovetic 23 £22,000,000.00
Andre Schurrle 22 £18,000,000.00
Andy Carroll 24 £15,000,000.00
Wilfried Bony 24 £12,000,000.00
Carlos Tevez 29 £12,000,000.00
Ricky van Wolfswinkel 24 £8,800,000.00
Jozy Altidore 23 £8,500,000.00
Iago Aspas 25 £7,700,000.00
Nacer Chadli 25 £7,000,000.00
Arouna Kone 29 £6,000,000.00
Dwight Gayle 22 £4,500,000.00
David Moberg Karlsson 19 £1,500,000.00
Duncan Watmore 19 £-undisclosed or free
Danny Graham 27 £-undisclosed or free
Nicolas Anelka 34 £-undisclosed or free
Stephen Dobbie 30 £-undisclosed or free
Andreas Cornelius 20 £-undisclosed or free
Nicklas Helenius Jensen 22 £-undisclosed or free
Yaya Sanogo 20 £-undisclosed or free
*If you add in EPL goals (last year) for these players, it's a pretty grim list. Tevez scored the same as Kone, but commands 2x the transfer fee. You can add Anelka's previous goals, but at 34 I can hardly imagine these factor into current production. Several players have scored at other top leagues, but all this to say that £6MM for 11 goals may be a good price, all the whining here notwithstanding.