Random thoughts- very influenced by my own situation and limitations FWIW
-really good hand plane isn't that much cheaper than second hand drum sander (at least here in Australia, a good Veritas smoothing plane is just under half the cost of the 16/32 you posted)
-time it takes to learn to use hand plane properly compared with your hourly rate
-ease to keep faces of timber parallel on drum sander compared with hand planing
-planer (and sometimes even excellent hand plane work) won't handle highly figured timbers as well as drum sander
-for that model drum sander in particular, paper changes are really quick and easy (less than 2 mins to change grits)
OTOH, hand plane is more "sensual", not noisy, not dusty and certainly more satisfying when (for me "if") you get the desired result.
Because this is your income, somewhere in the decision has to be a calculation Return on Investment - how much time you will save and how much that time is worth, potential lost $ if you get tearout on expensive figured timbers.
Hope this helps.