We have now opened a commercial services section here on the forum for registered users. If you have a Fabrik project that you wish to have someone work on for you, post it under Help Wanted. If you are an application developer and wish to earn some money helping others, post your details under Fabrik Application Developers.
Both of these are unmoderated. It will be up to both parties to work out the details and come to an agreement.
For running J!5.1 you must https://fabrikar.com/forums/index.php?wiki/update-from-github/ or include the new file manually https://fabrikar.com/forums/index.php?threads/joomla-5-1-and-fabrik-cannot-find-files-error.54473/post-285151 See also Announcements
It works for me in the list view with the same settings, so the output is $2,300.00
Do you have your screenshot from details view? In details view (when element is read-only) it seems that thousand separator and decimal point are not considered at all, regardless whether you have something in "Format string" field or not.
To format the number in details view you could use some jQuery in details_xx.js and in "document ready" function loop through all the "number" fields with "each" function and format them as you like. As this is pure jQuery, you will find lots of examples for that in Stackoverflow.
I guess you could call it a bug. I cannot see any solution except the one I wrote above without hacking the core code.