A better way to seek financial commitment information from a prospective client is to ask your prospect if a type service is planned to be a part of their allocated expenses. For example, Do you have a marketing budget for your project and does it include funds going towards a social media campaigns?
This does two things. It request information from the prospect so that you are able to determine if marketing services are being utilized or will be utilized in his/her project. Second, it allows you to plant the seed of encouragement regarding the use of your specific type service.
Never be too generic with "What's your budget" type of statement especially if you are not aware of your prospects project scope.