Ask HN: Cheap Document Signing Solution?

Does anyone know of a cheap document signing solution with API access? We have about 3,000 documents (1-2 page) per year that need to be signed by customers and emailed, that's it. We're getting quotes of between $2-4 per document from all the major companies. That seems very high to us for just requesting an electronic signature on a 2 page PDF. Anyone know of a cheaper solution for this one use case?

EDIT: We've decided to just build our own solution for this simple use case, it's actually not that difficult. We still don't understand how document signing companies are able to get away with charging so much.