The cheapest Miku wig I've ever seen was 58$ which included the shipping cost.
It had the extensions, the color was set.
I don't own a Miku wig, otherwise I could send it out xD
However, there are wigs similar to the Miku style you can find which range from 20-40$ and you can dye it the blue you want.
has a lot of great wigs.
Hope it works out for you