The manufacturing cost is emphatically not only 1% of the total development cost. Particularly for GPUs, the high bandwidth memory and manufacturing costs are a significant portion of the product price.
I have no idea what is the manufacturing cost of a 800 mm^2 die is, but I am sure it is lower than the development cost.
> Particularly for GPUs, the high bandwidth memory and manufacturing costs are a significant portion of the product price.
HBM is not manufactured by the GPU vendor, it is an off-the-shelf component that AMD buys like any other company can. Thus, the cost of HBM is tallied in the BOM and integration costs (interposer, packaging, etc).
[1] https://www.tomshardware.com/pc-components/gpus/spitballing-...