Mail on Big Sur does not reliably find dollar values
I can confirm this is a real issue since Big Sur. I did talk with Apple Tech Support, she agreed it is a known issue. She told me to put problem in Feedback Assistance which I did a while back. I have not come up with any work around other then just searching for numbers to left of the decimal point as you mentioned.
In addition, various text and text strings are not found as well. Really want Apple to fix this asap.