Rhum agricole blanc is typically not as expensive as high end Scotch to be sure, although they are generally more expensive than molasses based white rums. Of course most molasses based white rums aren't very good (at least to me).
But well aged rhum agricole, like the Neisson 15 or 18 (although Neisson, a smaller family distillery on Martinique, while very good, seems pretty expensive in general) or Rhum JM 15, are typically very expensive (and also can be hard to find). And are oh so goooood!
The sorry state of rum regulation is very frustrating. I agree with the idea of making the labeling be more honest but getting so many different countries to agree to a single set of rules, and rum is made in a LOT of places, doesn't seem likely any time soon. The economy of some small countries is largely tied to major rum producers and they aren't likely to do anything those massive companies are opposed to.
Rhum agricoles and in particular Martinique agricoles are a good bit more regulated and are not allowed to add sugar (although there is even some suspicion of skirting rules with at least some of those brands). Jamaica and Barbados (home of Doorly, Foursquare and R.L. Seale 10yo, all made by the anti-sugar rum producer Richard Seale. His recent Foursquare 11yo cask strength rum is superb!) also have rules about sugar in rum. But most places do not.
Sugar is rampant in rum and hard to always get the facts on. But there are places where the sugar contents of rums are listed. The ones from the Swedish and Finnish governments presumably are pretty reliable. I can't speak with certainty to lists on other blogs although since they are partly based on the government tests it seems they are likely to be fairly accurate.
Of course I could say as much with almost any spirit although rum seems to be the gold standard for having a lack of standards! But Scotch, American whiskey and other whiskey producers tolerate a fair bit of their own nonsense within their industry. I would love to see requirements for the DSP being listed on any American whiskey produced, regulations to require labeling of coloring in Scotch as well as more transparency with age statements in both of them. The mystery 9.09% rule in Canadian whisky that doesn't have to be disclosed seems like a lot of nonsense as well.
(I am going to have to start making sure I have gotten to the last page of the thread!)