I'm happy if that works for you. But your business strategy runs completely counter to the management practices of almost all successful companies in the world; not just internet ones.
Every company worries about minimizing customer acquisition costs. And social media is there on top along with newsletter/email marketing as the best ways to reduce this cost on the internet by building a community and getting your one-time visitors become repeat visitors. It's pretty strange that you choose to rubbish away a great opportunity simply because your business doesn't seem to need it..
I'm not here to convince YOU to spend time on FB. For that matter, I have not spent time on social media marketing myself. But I assume this thread is all about exploring a new channel by seeing how it has worked for those who have tried it.