A buddy of mine, a prominent and successful sales guy, shares a story:
A successful and respected executive and long time customer calls him and asks him for a deal on his product, claiming it's for business use. He gives her a great price. A GREAT price that only her influence as an executive in a huge company could get. It doesn't take him long to learn that she has used her connections to help a personal friend get a corporate price on a personal purchase. There's no business connection whatsoever.
I asked him what kind of deal she'd have got if she'd just been up front about it. It turns out he would have offered her if not the exact same deal, a very good deal.
He forgives her; my buddy is a Catholic businessman who walks the talk. He just doesn't trust her, quite another issue.
People lie for only two reasons: they're embarrassed by the truth or they're afraid of the consequences of telling the truth.
Either way, that's no way for grown ups to live. It's certainly no way to treat a friend. It's no way to do business.