I did a quick check in a demo 6.2 b2b, patch 12.1, and I was able to set a sales price for a sub product. This demo catalog. had only the test data installed.
The was a bug in the admin for a long time that did not add a sub products to the categories to products table. SO if the sales price is not working I suspect the sub products did not get entered into this table.
Although this bug has been fixed or going to be fixed in later version 12.1 does not have it.
the fix does not put the missing data into this table. I would say that a special routine would have to be code to check to see if any of this data is missing and add it to the categories to products table.
Tom