I would not immediately assume bad intentions of the garden landscapers who do not respond. Yes, that is poor style, no question about it. But as a garden landscaper, you also first need to have the appropriate machines and the corresponding experience with a steep wall in order to be able to implement your wishes. Another reason could be that the garden landscapers simply assume they are writing their offer for the trash bin because you will not buy at prices around 200,000 EUR anyway. Over time, you develop a feel for whether the customer is aware of what their wishes approximately cost and whether they will be completely shocked by the offer. Then the work is not worth it.
Have you checked what your 23m basalt palisade alone at 150-180cm height costs? You will easily spend 500 EUR per meter just for material, so almost 12,000 EUR. Plus foundations, earthworks, drainage, etc. That is easily 30,000 EUR executed by a professional.
I have been struggling for months with a garden wall just under 1m high made of concrete paving stones to catch 50cm in height and have already sunk a good 5,000 EUR in material for almost 30m...
The material alone for your project will break into six figures because everything is supposed to be extreme and, of course, natural stones.