Assuming that money would be the motivating factor for your boss not to want to do it, then.. if you explain that by giving your software to the open source community, it will be tested, reviewed, and quite likely improved if necessary. This should save him money.

Of course, open source software allows all of us to save time by not re-inventing the wheel, by sharing resources and knowledge, and in general, working as a team (business buzz word = synergy).

Good luck.