The number value for each cell is coming from an IF formula:
=IF(C2="Short Sleeve","$10",IF(C2="Long Sleeve","$15",IF(C2="Sweatshirt","$25","0")))
So in each cell in the column, there is a currency value listed of $10, $15, or $25. These cells are formatted as a currency as well. I've also tried removing the $ sign in the IF formula and formatting as a number but neither work. So I assume that Excel
recognizes the "$10", "$15", or "$25" as text which is why the Sum function won't work. However, when I add each cell individually (i.e. A1+B1+C1), it works fine. Here are some pictures:
IF Formula:

SUM Formula does not work:

Arithmetic does work:

Any thoughts?