I tested this and the game does not seem to be able to track all of the earnings that you make from wellness over time with the way it has been set up.
The objective tracker is looking at simoleons earned for one iteration / one single transaction. So essentially it will complete if you are tending a massage table or massage chair, and earn 5000 simoleons in one go. Which, I don't think is even possible with massages, because no massage or manicure gives 5000 simoleons for a single pop.
You can test this by having a sim tend a massage chair or table, and then sell an object or stack of objects from your inventory for over 5000 simoleons in one sell action - so a stack or multi-selection of high price selling goods like dragon fruit should do it.
The game doesn't seem to be able to retain any incremental progress using the test method it is using - so for example, if you earn 2500 while tending a massage chair, twice in a row so that in total you gained 5000, it doesn't work because the game notes that you got 2500 for the first transaction, and then forgets and resets the counter and begins tracking again from zero for the second time. And if it works like this for goods selling (which it shouldn't really, but the game doesn't seem to be able to distinguish income sources), then you can guess it works this way for wellness paid services too - it is only tracking one payment, then resets if it wasn't 5000 or over.
If anyone playing on PC/Mac and is ok with using mods, I have made a mod for this issue that works by replacing the test used for the Hustle objective with a different method I copied from the way the game tracks donations received in the political activist career. You can find a link to my mod site in the Common Game Fixing Mods post. It's called "Wellness Aspiration Fixes".
