Originally Posted by
viajero boricua
The problem to figure it by the rate given is precisely when temporary offers, such as the one you've exposed with IHG (3x normal). You can't accumulate at the promotional rate all the time (not only that, but you can accumulate for IHG stays / purchases, but you can't use MyP's for that same company), so the best way to figure the value is from the reward point of view, not what you accumulate with. Then you can compare with other ways of accumulation, like credit card purchases...
15/$ may be temporary, but it is frequent enough to use by planning ahead. Any analysis of value for reward is first to "cost" the acquisition of the point then do the math for the points required to redeem.