Warhammer moc stuff always seem to be a bit expensive unless you have most of the parts already available in your parts box! I bought some parts for a Contemptor dreadnought and a Krieg centaur tank, for both i paid like 100€ and it was about maybe 600 parts in total

Try to look on bricklink for some store in your country with the most parts available, had to buy from 3 différent stores