I get your logic but Austin's career seems to be on a downward spiral and he doesn't fit under Wilders ideal player type - i.e. someone up and coming and with a point to prove that they are good enough for the PL. Austin's already achieved in the Prem and being called up for England.
Saying that, Wilder has signed experienced players before such as Richard Stearman but I'm not so sure that Austin will be someone we'd go for. Madine does fit more into Wilders mould as someone no doubt desperate to play PL football but that's not to say he's a better player than Austin. I was really impressed with Madine last season but I do accept if he costs £5m then you can argue a case for other players in that bracket, but I can't name a target man who is as good as Madine that you'll get for under £5m from the UK, I reckon Austin will cost more on wages than Madine.