There is also the possible diplo hit though, from AIs with Buro as favourite civic. Like in my current game, with +3 and +5 for Buro. I did wind up going out of it for Nationhood and drafting rifles, but if I hadn't planned war it would have been difficult to leave Buro.
On the math, you should only take base commerce * 50% right? The other multipliers apply anyway after all, so the difference is the +50% with Buro.
Edit: And same for hammers of course. I find that can be a bigger deal than the commerce at that point, and the loss in hammers can be pretty severe in the capital. Those hammers can of course be used for Wealth, which makes the actual loss to research/wealth bigger than first assumed.