My experience is completely different. [...] Both offer fixed house types; if you choose one of those and stick to the standard, the price/performance ratio is really good. [...] Freely designed houses were exorbitantly more expensive. [...] But exactly that "a bit more here, a bit less there" deviates from the standard and then a price under €300,000 was immediately obsolete.
What I meant was: in the past, "prefabricated house" long meant "standard house," and even with solid construction (cooperations) there were such. Drawer plans and fixed prices went hand in hand. That also had advantages, not least due to routine in the execution of the "critical points."
Then "free architectural planning" became a sales argument in fashion. This increased the "pressure" to abandon the 62.5 cm modular grid, which is now implemented everywhere in today’s production facilities.
A few years ago, there were then two further upheavals: one had to do with energy saving regulations. All standard plans would have to be redrawn anyway for new wall structures. Especially for passive houses, which, from a constructional point of view, are somewhat boldly spoken occupied air conditioning systems – quite a drastic paradigm shift. Together with the fashion taste of a new decade, this would have meant that often not even the previous bestseller "unchanged" would have remained from the existing model ranges. So: "back to square one." Thanks to the increased share of individual planning and the faster implementation in CAD, most house manufacturers (now also the solid construction faction) have said goodbye to the standard program. In its place, many "building proposals" have stepped in: i.e., examples of plan-calculation-"products," whereby the two factions do not differ much in their attitude toward loss leaders.
The second big upheaval – which happened roughly at the same time – was then the market concentration: with generational changes in the owner families and in production processes, there were "market cleanups" & "mergers," as already seen with food, breweries, and water bottlers. What has "survived" are often "brands with a good image," behind which the founding family is now very rarely still standing.
Overall, prefabricated construction and solid construction providers have largely aligned with each other. Aside from objective or subjective reasons to consider one construction method better in individual cases, both are increasingly comparable "building contractors." And that is what they have become, numerous portals spit out "suitable" providers of both denominations for entered house sizes and price ranges.
Harshly said, both offer "only" the structural house behind the insulated facade.
They have also become more similar in price: where houses used to become more expensive in prefabricated construction according to the parameter "house size or wall location," and in solid construction according to the parameter "deviation from the preprinted construction service description," this "assignment" only applies to a limited extent today.