I do not understand the process as if there had been an offer "years ago," but rather a current offer (May 14, 2018) that was corrected a few days later (May 25, 2018) for the price increase of the last 3 years (since 2015) and then in September 2018 additionally the price increase of the period up to execution (March 2019, i.e. 10 months after the offer) was anticipated and factored in.
That is exactly how it happened.
At the owners' meeting in August 2018, only a cost estimate was presented.
Unfortunately, with the construction project – due to our own stupidity – many things went wrong from the very beginning.