With us, there were differences of €40k despite largely the same construction service description. When we then asked the more expensive one what was different with them (we would have liked to give them a chance), they just ranted against the miserable Polish pack of the cheaper provider and said the roof gable wasn’t even properly framed. Well, the "Polish pack" excellently raised the walls for us. They worked absolutely professionally and cleanly, and the roof gable survived Fredericke perfectly.
We also asked the cheaper one why: They are significantly larger and can achieve a lot through mass orders. In addition, they apparently have good control over the craftsmen with their market power (our assumption).