Increase this to 50 plus 5 attrition aircraft, and it starts to make a lot of sense, particularly at USD$116 million per unit or, better still, a lease/buy, with the purchase dollars spent in Australia!
As for STOL or STOVL, this is a feature Australia does not need in our air combat capability since it is contrary to Australia's fundamental strategic needs of persistance, range and speed, with systems being a given, since they come with new or can be readily achieved through upgrades and other technology insertion programs. The latter is something some Defence folks are scared of because of their cultural cringe and aversity to managing risks (or, as folks in Industry say, doing the work).