It's ALOT more trouble to take the roof off a coupe, and then you still just have a roof off, not a convertible!
I've had convertibles in c2, 3, 4, 5, 6 and now 7. Added weight? Not a big deal! Top getting dirty? Not a big deal! Price difference, not much in the grand scheme of things.
So I don't "just get a coupe" because...well, because I love a convertible!
A vette friend went with me to look at c7s and wanted me to take the top off the coupe to see if his wife could do it. I did it but no way do I want to do that every time I want to drop top!