There does not appear to be a way to determine if a cell is bolded
using the built-in functions of Excel. However, you can use VBA, see

http://www.cpearson.com/excel/colors.htm

An alternative to VBA is to use an adjacent column to hold the
indicator of the condition that causes you to bold the prices. Say you
put a 1 in that column and use Conditional formatting, if you need, to
also bold the prices if the adjactent column equals 1. Then you can
easily use SUMPRODUCT to sum those prices that have that condition.

However, this approach will not catch prices that you explicitly bold.
Nevertheless, it might help usability if the reason for bolding were
obvious in an adjacent column with an appropriate header.

HTH

DOR