I do understand your frustration, and I see your point.

Without knowing how much work had to be done to support higher resolutions, it could be argued either way whether the result was more of a patch or remastered version (with the change list certainly looking more like that of a patch). However, people that have been following the forum for years are less likely to assume that Larian has suddenly become a bunch of greedy bastards. Without some evidence or pattern of behaviour to the contrary, we would be more likely to give them the benefit of the doubt and assume it is legitimately a remastered version, or that they have some valid reason not to release a patch. Or at least more likely to figure US$5 or 6 is not that big a deal for an updated version, even if (in someone's opinion) it should have been a patch.

Making a patch wouldn't require massive resources, but given the fact that there was one person working on the remastered version, the additional resources it would take may not be considered worth it. I would guess the reason for not releasing a patch was less likely technical (or financial), though, than political or other.