I just tried it on an MC9190 CE with DW 3.7, and it worked for me. I went into Basic Configuration/Basic Format/Prefix to data and Suffix to data and set them both to $. Also made sure that the is a checkmark next to "Enabled" in "Basic Format". Then I go into wordpad and scan a barcode and I see the $ characters before and after my scan.
I tested Data Wedge 3.6.10 on a MC92NO CE7 and it worked with the $ prefix and suffix. I have attached the DW config. Are you using CE7 or WM653? Either way, place the attached files in \Application so that the folder structure is\Application\DataWedgeStoredConfig.