Architectural office obtains quotes only from long-standing business partners

And the reputation... it is completely overrated, 9 out of 10 builders do not inquire about the reputation when they build, that is purely the bubble opinion of those who are active in this forum.

That may be true. But a Dullie-quote of 90% would be quite extreme in my opinion.

Above all, it is exactly the opposite: in the section "Erfahrungen mit Baufirmen" people who otherwise have no overlap with the community as a "bubble" ask in nine out of ten cases almost only about the reputation of a particular company and how "genuine" it is; less often about alternatives (= competitors, or entirely different approaches than going to GU X or Y based on reputation).

Hello everyone, now we are at the tender stage and our architectural firm is obtaining quotes only from long-standing partner businesses (two to three quotes per trade). They said this is the only way to achieve the high quality standard. What do you think about this? Is it true that you get the best quotes (price/quality) from local tradespeople you have known for a long time? I am just afraid that the architectural firm is not only working in our interest but also looking out for their partner businesses.

Our architect did something similar. In some cases, there was only one offer and it was quite expensive... If it was too expensive, the architect did not request alternatives or only did so reluctantly... We then found craftsmen ourselves through recommendations and awarded the contracts together with the architect or sometimes on our own. For example, our architect wanted to commission an engineering firm for planning/tendering of geothermal drilling/heating, ventilation system, underfloor heating, plumbing, because he lacked the expertise. We then awarded the planning separately to a heat pump specialist company and a plumbing company and saved more than 40,000. But it cost a lot of nerves because you have to find a replacement at short notice so the construction can continue... Basically, the craftsmen from the architect worked properly and are still easy to reach after completion. If there are problems later, it’s good to have someone local on site. (e.g. windows, electricity, plumbing...)