I think it's impossible to really estimate how much an energy costs, because you could argue that you need to include the cost of potential accidents or the incertity of raw materials costs or the cost of not being able to produce energy when you need it, etc.

For solar, you need sun, for wind, you need wind. The real issue to solve is being able to store electricity. Once you have that, a lot of issues disapear, because you can procude when you can, consume when you need.

In the long term I really think nuclear is optimal, after all that's what the universe chose... In a way, solar energy is fusion based. ;)