The engine that they use are that which they put in caterham models, r300,400 and 500 (r500 being 253bhp N/A, basically fully forged and 8500rpm rev limit, fully balanced everything!
Alot of the money is for the manufacturing process
i built mine for less than 8K the crate engine your paying for more than the parts value ie cosworth running it in and men in fancy white onsies with goggles and F1 style builds.
least im halfway there with the mtx75 beign currently fitted by amd, £2500 later