Value of the murs?

This follows on from an earlier thread before. I’m seeking your valued opinion.

I spoke with mairie about change of business use (destination) and there seems to be not too much of issue from a garage/mechanic into a yoga studio. I’m now checking about contamination.

Now the owner is selling his fonds du commerce (let’s say 200,000 euros) and the murs (let’s say 250,000 euros). The whole thing is for sale at let’s say 450,000 euros. Now the fonds du commerce is of no interest to me - I do not need his clients or equipment. However, the location is prime real estate for my business. It is just one big warehouse (although work is required!) on a very good street. Perfect. However, I am aware I could potentially build an apartment on top floor as the building is quite low in height compared to neighboring buildings (it is 2 storeys shorter) to the two adjoining buildings.

This question is about understanding the French mentality and doing business here. Is it unreasonable to offer more for the murs (because you see the potential for a nice bigger development for studio and residential and because of its prime location) - assuming other people might be interested in doing the same. Or should you only offer the price of the murs and never go higher because you are only after the murs and so it is not how business is done here. Am I making sense?