With current example on file, pls refer to sheet 1, J16 cell it has 8.597,77 which is "text" and not "number", because of "," in it.
in case you remove comma, it will reduce the decimals to 2 positions and value is changed to 8.60
to retain 8.59777, increase the decimals in formatting.
Once you have this done, the above said formula will work.
Now, you may use find and replace window to change remove all ",".
See attached file, and pls do check for values are correct in sheet 1.
I have just copied your formula and multipled with c21% like
= YourFormula + (c21 * YourFormula)
I also believe there is good scope to simplify your formula and also to include mark up % in price.
Regards,
Prasad DN
PS: Culprit is ","s in sheet1 making all mathematically formula fail.