The problem is that even in the futures market for 2025 it isn't predicted to cost that much (in today's money). Even with the predicted decline in supply.
The return on equity predicted for EDF is 20% to 35%. That is an incredible sustained margin to achieve over decades.
Predicted, predictions are almost always wrong. No one predicted oil at $150, and then when 'peak oil' was the buzz word no one predicted oil at $27, but we got there pretty quick. No one has any clue what so ever of what future energy prices will be. What happens if Iran / Saudi decide to stop messing around with proxy wars and actually try to annihilate each other head on? Oil at $300 a barrel. What happens if we have a period of global peace and stability twinned with greater technological advancements which mean that US shale producers find ways to extract oil efficiently at $10 a barrel??
We simply do not know, and anyone who tries to predict these things is taking a risk, especially when building a nuclear power plant on the back of those predictions. If your going to take that big a risk, you want to be duly compensated for it.