This diagram explains a simple geodesic fact: you double the geodesic dome diameter, you quadruple the interior floor area. For those who plan to cover their geodesic dome, the same rule applies; doubling size results in quadrupling area.
One way to limit the additional costs when making the dome diameter larger is to “truncate” the original dome design; this means to use a less than the traditional 1/2 of a sphere which you see most of the time.
Truncating will reduce the diameter of the dome, but not significantly, if for example, you only remove one row. Your ceiling height will be less and you will save some money by using less material. Note that if you do not use a flat base calculation, your base will not sit exactly flat on the ground. The Kruschke calculators on Domerama will give you different truncations while keeping a flat base.