Dembele is scoring at the rate I'd expect Janssen to in Scotland so I don't think he's worth spending big money on personally. A striker would need to be scoring 3 or 4 goals a game in that dog shit league to be worth spending money on IMO.
Prepare for the lazy comments about Van Dijk or Wanyama excelling in Scotland (neither of which are strikers), and forgetting the likes of:
Gary Hooper
Broken Robbie Keane
John Hartson
Scott McDonald
and a whole host of other strikers who they played like Messi at Celtic, and yet suspiciously like Altidore everwhere else.
I'm not sure there is an example of any goalscorers who were prolific in the SPL, and yet found their level (or even didn't) in the Championship/Division 1.