Given the figures are astronomical employing a quantity surveyor to view the property and the consider the nature and cost of the works proposed would be Worth every penny and in the end save you a fortune.
It depends on how you propose to approach it.
You do not want to say something which later your expert cannot support or agree something that your expert may later say that you had no need to agree.
But you could argue in broad terms saying that is too high without being too specific and see whether they change position.
You can suggest a meeting if you feel it will cut through things but first I would get the QS comments in writing on the estimates.