Increased production costs associated with increased output produced? Why do firms have prices increase with the SRAS or Supply Curve?
this is for SRAS and AD, but I'm also going to apply this a bit fo microeconomics.. sorry for mixing, but my question applies in both ways, I believe

You are applying market equilibrium logic to the supply function. When aggregate demand shifts for some reason while the supply function is unchanged the equilibrium price will change.
If the short-run aggregate supply (SRAS) function is upward sloping then there are no economies of scale (in the short-run). This does not give you detailed information on what a firm is able to do long term.