If we assume that the economic model of CPU manufacturing is essentially - very large upfront costs in R&D and improved fabs - The marginal cost for each addi

If we assume that the economic model of CPU manufacturing is essentially - very large upfront costs in R&D and improved fabs - The marginal cost for each additional CPU manufactured is, in fact, very low Then, isn't this pretty much the textbook example of a natural monopoly? I.e. in such a case, if the market was spread out over more suppliers, would the customer in the end pay more due to the vendors amortizing the R&D costs over fewer units sold? Vs. the current situation where customers are paying monopoly prices to the incumbent vendor.