There are only 3 or 4 companies for the fittings anyway ^^
The carcass elements don't determine the price in normal kitchen construction. They are always made of particleboard and no one can really demand huge sums for them. Money is made on the electrical appliances, which all have massive discounts due to the internet (RRP 2500, for 900€ online). And of course the fronts, which cost money depending on the design.
You get the cheap and at the same time best kitchen if you:
- order the electrical appliances yourself online
- get carcass elements from somewhere else, e.g. IKEA or whoever sells the elements individually
- get fronts directly from the carpenter
- get fittings directly from the manufacturer, or an intermediary (or from the carpenter)
- get the worktop directly from the stonemason (if you want granite / these are the people who sell gravestones...) or carpenter or even buy it yourself at the hardware store for simple shapes
- order various other parts like handles, sink + faucet, waste system online (costs only about 30-50% of the RRP there)
- do the assembly yourself
Every intermediate step is paid for expensively. The granite worktop from the kitchen builder costs twice as much compared to buying direct, even if the kitchen builder orders the worktop just there. The 10 cent fittings are sold as luxury for 20€, because some 1 cent spring damps something. etc...
A 15,000€ kitchen (after discounts at the kitchen studio) from the kitchen house quickly becomes a 7-8000€ kitchen
The problem is clearly that you have to do everything yourself and some planning is required.