Ask HN: Patents for startups?

I believe to have found a patentable software methodology. I consulted a patent attorney, and learned that a provisional patent application costs $3000. A year later, non-provisional application would cost $15000 + filing and drawing fees, coming close to $20000 per patent in total. Currently these costs are prohibitive, but on the other hand it makes sense to apply to protect our IP.

Do you have any experiences with applying for patents as a startup? Is there a workaround to avoid these costs? How good would a DIY patent application be?