Plastic I am sure. 3A does some great work. Metal Gear Rex and Ray are from them and I LOVE them. So this Megatron certainly has me wanting it. Gonna guess 400+ USD though.
For those interested, tomorrow around 9pm, Megatron goes live on Bambalandstore.com
Bamba version is cloth and matrix. Retail is I think just Megatron, so if you want that cloth and Matrix, order from Bambaland