SpaceX founder Elon Musk said... if you can recover a rocket, it means you're not throwing away millions of dollars' worth of hardware. Launches would cost a fraction, perhaps a tenth, of what they cost now.They've reduced launch costs already, simply by re-inventing some wheels in-house. Naturally it's hard for me to criticize what he's saying, because he's shown he knows what he's doing time after time, but IMHO the fact is, payload costs will go up with this part of his approach, because the mass budget for the payload will go down. The workaround will have to be, using more rocket than would ordinarily be needed, in order to orbit the same payload while also carrying the fuel for the landing.
Except that he won't be throwing away several thousands of pounds of aerospace hardware with every launch. Which do you think is more expensive, a pound of missile or a pound of fuel? By your logic it would be cheaper to by a new plane than load the fuel to taxi back to the gate.