Price increases in construction contracts related to Corona

This morning we learned the following from a carpenter in our region in South Bavaria:
The regional timber construction companies and carpentries are increasingly experiencing problems in production planning and cost calculation due to the massive increase in wood prices and delayed wood supply. Apparently, a large part of the wood goes to the USA for high prices.
The carpenter is in contact with some regional timber construction companies and has now learned from some of them that the hardly calculable additional costs are partly and newly passed on to the customer in the form of such clauses (must be), otherwise it becomes existentially threatening. He did not know these clauses from previous years.
From our in-house calculation, we calculated a wood share of about 35% of the total costs. Thus, with an increase in the wood price of 5%, we arrive at an additional cost amount beginning in the five figures. Of course, we do not find the possible cost increase nice or acceptable, but what alternatives are there now if it is similar with other regional companies in the end. We did not want a big name in the timber construction industry (still with fixed price guarantee here?), that was partly like the vacuum cleaner salesman ("just sign here and everything will be fine"), opaque and not cheaper, with the regional provider we feel a thousand times better taken care of. However, we are already asking ourselves whether the current development does not even endanger the solvency of the small wood suppliers through large projects with fixed prices from previous years (in the performance contract, 8% down payment upon signing the contract is not nice, but weatherproof shell at 52% payment progress).
Somehow we caught an unfavorable time: wood prices rise massively, wood for local companies becomes scarcer, house costs are not securely calculable, construction interest rates rise, and the apartment is becoming far too cramped with the children.

The little one communicates the issue, the big ones either added 15% or on page 5, 2nd column middle in the fine print there is a similar clause.

Especially when buying a house,

It will affect other trades as well. When I look at the development here since Christmas. Something like this has never happened before. Price increases of up to 30%, sometimes just 8 weeks after the last one. Delivery times are unpredictable. Whether steel, hydraulics, electrical or paints. Stock items suddenly not deliverable.