I am designing a form having multiple stages where user 'Confirms' the quotation at the last stage. While thinking about how to prevent user leaving this last confirmation page (before he actually confirms), I thought of "Are you sure you want to leave this page" popup message. I got mix opinions through stakeholders whether showing this type message being ethical or not. This keeps me thinking what are the other ways of achieving the same?
Note: Doing follow-up through through email for incomplete task, is a different thing, and I look at it as a supportive backup option. I am looking for on the spot solution which will save our time and increase conversion rate.