I was wanting to compare the industrial scale cost of doubling the width of a pizza to doubling the width of the cross section of a starship. Your entitled to you're opinion
OTOH, the weight of the rocket grows mostly linearly (it's essentially a skin around propellants), the number of engines grows with the square of the diameter and the fuel volume grows at a cubic rate, so the engines can burn for longer (at some point, aerospike engines will become practical).