To clarify, the issue is not that there are formulas in the cells, but that some of your cells are returning errors due to the MATCH function not being able to find a match. You can "trick" XL into ignoring the errors using SUMIF. Something like this should work:
=SUMIF(A:A,"<1e99")
The 1E99 is simply an arbitrarily large number. It's just there to force the function to only look at numbers, and ignore the errors.