We have credible quotations for the flyaway cost and don't need indications, or interpretations, from unrelated deals.
We know that India paid around 91 million USD per Rafale F3R and we know that the US pays 70 to 77 million USD per F18 Block 3 in the next 3 years.
The Base production cost of Rafale is higher, there is simply no way around that fact, just as the cost per hour is higher compared to Gripen E and F18, as proven in Brazil.
You can even add the lower weapon costs of US arms, vs European once, that will further reduce the operational costs, or the commonality of engines with LCA MK2. The Rafale is only "cost-effective" compared to the EF.
So when the aim is maximising numbers, from an already restricted budget, cost per unit and per hour will play a crucial factor.