Can companies afford NOT to?

For the past few months I've been involved with some business ventures in the Rewards, Loyalty and Incentives space. The idea of giving something to someone to get them to do what you want (or in some cases what you don't want). Motivation is what it comes down to, and the industry has found that you can motivate sales people with tangible rewards of 2-5% of their sales. But how do you measure the 'worth' of something less quantifiable like taking a sick day, taking a personal day, or booking vacation at inopportune times? For those of us at the level in our careers where it's not the end of the world if we take a personal day, bully for us; but for the rest of the world that needs to work to make money, what is the 'tipping point' of tangible and non-cash incentive that will make you decide against slacking off and missing a day of work. Comments please... Also, I'm starting a Rewards and Loyalty blog, and I'm going to try to put more relevant industry articles and writings on it, but feel free to point me to things you've read that fit.