I believe him. Otherwise, he has everything in the house made from very noble materials. Even the tiles in the garden, etc., are fancy. And when I look at other gardens on the internet, where a budget of 250,000 € is sometimes stated without there being a designer stainless steel pool in the garden, I find that quite credible.
Well then, tell me where the 200k is going, besides the water feature. A few slabs on the terrace don’t make it, or are there 400 sqm lying there? Of course, it could be that the neighbor paid 200k, but the thing could also be had for 80k. Some people also believe that our house cost 700k, but actually, it was much cheaper. The same people pay 400k for a 140 sqm dump with laminate, ETICS, and interior doors from the hardware store.
Therefore, I can only recommend: get at least 3 quotes, compare and negotiate.