You're not being specific enough to comment on the price.
Is it flat/pitched/gable/hipped roof, ...?
Are the posts 50x50/cold rolled/100x100 powdercoated...?
Type of roofing...?
Site conditions/access...?
Not that im necessarily asking you to answer all these questions, but there is more to the price than just a figure.
It works out to aporox $180/sqm...thats pretty cheap in terms of any roof structure to be supplied & installed i rekon...
BUT yes...Stratco are expensive...!!
There is also the salesmans wages & commission, production, clerical & transport staff just to name a few whos wages all need to be paid as well...!!
And dont forget about plans to council for developement approval & associated fees...
Always cheaper to do it yourself...but only if you do it right...
The man who knows everything, doesnt really know everything...he's just stopped learning...