This is the situation we're in now. Just different people shoulder differing amounts of the cost. Equal pricing won't change the fundamental economics of drug research.
Cost-shifting is a valuable effect in the pharma industry, because high profit-margin technology might subsidize low-profit high cost drugs.
Price differentiation is usually net positive effect, but being inequitable people have a reaction against it and more so in health related services. If you could only sell 1 type of seat in an airplane, for example, you would have lots less flying than today, by reducing the amount of rich people flying business/first because of loss of quality, and by reducing the median/average person because of increased cost.
So yes, from an economic standpoint, equal pricing has an effect on the research and development of a product. This should be obvious in this community, for example, look at Google. Almost everything loses money but search. Equitable pricing would make search cheaper, and all the other services paid.