$60k is a lot of investment simply to test a concept, and would be a luxury out of the price range of most small businesses, let alone individual entrepreneurial subject matter experts who want to build a product - even really committed ones with money to spend.
Assuming you actually want to win the business, why not pitch a much smaller project to help them tease out some mockups and build 1 or 2 of the main application flows to MVP level?
This wins you the smaller engagement now with the likelihood of the bigger piece of work once the customer has been away and shown the concept to customers.
This is why I don't really like these $2k and $5k MVP packages that people are pitching on HN lately. Your iterations should start with mockups rather than an MVP.