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...

Also, I've usually (more than 90% of the time by my demographics) don't do the whole surveys, so it's the 5 MyP for a few seconds worth of computer time (full surveys are NOT a good value in ANY system they're offered).