In my opinion, it is possible to get a house with land for €300,000. Of course, this depends on the size and location of the property. This project also requires a lot of time and effort from oneself.
After we turned away from the prefab house companies in June last year and collected offers ourselves, compared them, attended appointments, and conducted negotiations, we only then realized the price differences for the same materials and services.
If my father had not been on phased retirement, we would never have managed it. All in all, the search for offers took 7 months; we have been building for one month now. What you should definitely not do is immediately accept the cheapest offer. It is better to go to companies with a good reputation with the different prices; if they still have capacity, they are usually willing to make a price adjustment.
Regards Michael