You are seeking the right audience who knows how to appreciate the opportunity to invest in your product. You also have confidence that the right audience is out there. You just have to find it. Even if your book is published by an established company, the author's part in promotion is vital for the life of the book. Consider how other books like yours are marketed.
Many educators write educational books which are carried by educational catalogs.
Other specialists find a welcome audience through national groups dealing with their speciality area. Some people have found that selling online is helpful. Take a close look at the marketing methods for your type of book. This is often the first question people consider about self-publishing. I suggest that it should be considered only after you have satisfactory answers to the other questions.