Revenue value not showing up in confirmation page?

I am working with a client trying to get revenue reporting for Google Adwords. Here is the source code they have on their confirmation page: http://i.imgur.com/Y9Ht8X2.png

Which for our other clients work perfectly, the main focus here is the conversion_value line which should populate with the order amount.
However when running a test order, on the confirmation page the dynamic variable ends up blank, like this: http://i.imgur.com/KbCdCz7.png so we are unable to capture revenue in Adwords.

Any ideas as to what could cause this?

What's also odd is they have other trackers on there, and that line of code populates what it should, e.g. "53.37" for an order of $53.37.