Your string has thousands separator, so you need to strop that in order to convert to float:
total_cost += float(cell_value[1:].replace(',', ''))That said, probably your code can be simplified
If you can't explain it to a six year old, you don't understand it yourself, Albert Einstein
How to Ask Questions The Smart Way: link and another link
Create MCV example
Debug small programs
How to Ask Questions The Smart Way: link and another link
Create MCV example
Debug small programs