The setup for the article theorizes on the cost of lying on the person's stress levels. I'm sure that's a factor, but I think that pales in comparison to the empirical evidence the author has found in her own life -- the benefit of transparency.

There's an episode of How I Met Your Mother where a character always asks "Where's the poop?"[1] when she can tell someone is lying. She had a dog that always made he same face when it was hiding that it had pooped in the house.

I think the truth is that we all know in business there is always some poop somewhere. Whenever we lie, we leave our audience with an uneasy feeling, wondering what the catch is.

When we come right out and tell them what the catch is, we get past that barrier, which builds a relationship of trust from the start and allows the audience to weigh the values of our proposal on its true merits. This is the real power of telling the truth.

[1]: http://how-i-met-your-mother.wikia.com/wiki/Where's_the_poop...