Costing and price that changes after reopening the file

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I have a part that I converted into sheet metal so that I can use it in costing. So it creates two bodies in the list of welded parts (image1)
Image1

So I exclude the one I don't want and I take the sheet metal model (image2)

It gives me a price (7.22€) using the sheet metal function, so everything is fine (image3)

But if I reopen the room the price changes (picture4)

It's the cost of manufacturing that goes up, any idea why?

Thank you