Chaos Communication Congress had (has?) a model where regular tickets were priced very reasonably, and there were special "business tickets" that were marked up by a factor of 5 compared to regular ticket prices. The only difference is that you only get an invoice for a business ticket, so attendees who have their costs covered by a company need the business ticket, while individual attendees benefit from lower prices.
I don't know how invoicing works for a web service, but maybe that would be a model to consider? Keep the low price point for individual users, but use a lever like this to add some considerable markup for companies purchasing your services.
