I fully agree with the logic that the OP uses, with one small addition or caveat.
The lingering question is "How much am I willing to pay to feel spoiled?" Again, that comes down to personal habits and preferences. Some are willing to pay a large amount for suite accommodations with limited access areas, etc. On the other hand, on OV cabin is fine and we will "splurge" on a balcony depending on the itinerary and cost.
For us, the Plus package is marginal at best from a cost standpoint. Obviously, tips are required and we usually get an internet package to communicate with home. That covers a little over half the cost of Plus. After that, we can "splurge" on an extra drink, fancy coffee, or fancy dessert.