For sure, sometimes it makes sense. However, I just wanted to clarify that you need to actually do the math and not just assume that a $100 credit is an absolute winner.

And if staying at a property where a Platinum already receives breakfast (which the OP stated they are Platinum) the math for your stay gets less interesting and at least for me has to be weighed against the hassle of having to go through a travel agent to make/manage the booking. For example, if you already get breakfast as a Platinum, that benefit is neutralized. Then, taking the higher end of your rate example (i.e. $30 more per night) over three nights, that is $90 extra dollars you are paying to get a $100 credit. Net savings of $10 which for me wouldn't be worth the hassle of dealing with a STARS agent. Further, I can use the $90 in my pocket for whatever I want, not just what the credit is annotated for.

Now obviously, if one is not Platinum, then getting breakfast can certainly make the math better (or if its a property than doesn't offer Platinums a "full" breakfast).

Regards