ᐅ Which prefabricated house provider offers the best prices and experience?

Hello,

we unexpectedly have the opportunity to purchase a plot of land. Since it comes from family, the price would be a real bargain for us, around 200 euros per square meter (about 19 USD per square yard) (Bavaria - Baden-Württemberg border area).
Unfortunately, the plot is not perfectly shaped; it is 13 m (42.7 ft) wide and 23 m (75.5 ft) long, so roughly 300 square meters (3,229 square feet) in size.

This weekend, we visited a large model home park and checked out various builders.
We were especially impressed by Baufritz, Weberhaus, Schwabenhaus, and Gussek Haus.

I wanted to ask for your experiences with these companies—maybe also regarding costs?
Our budget is about 450,000 euros (around 478,000 USD), minus the land cost leaves us with 390,000 euros (about 414,000 USD) for the house and additional building costs (the plot is already serviced). Our idea for the house is about 130 to 140 square meters (1,400 to 1,507 square feet) of living space, with a footprint approximately 7 m (23 ft) by 12 m (39 ft). We plan to do the landscaping ourselves; a garage is not planned for now, and we also do not want a basement.

I would really appreciate any suggestions!

PS: No, we do not want to buy and renovate an existing property. On the one hand, there are hardly any available here, and on the other hand, it is outrageously expensive when something does appear (recent example: semi-detached house, built in 1969, no (!) renovation measures since construction except for windows replaced in 2012, mold in all rooms, 400 square meters (4,306 square feet) of land, not in a city but in a village, sold by bidding for 380,000 euros (about 404,000 USD)).