When I was trying to convince my DW (took over 2 years), I used the 'death by spreadsheet' method to convince myself and dropped little hints about how encouraging that was going. Then, I turned to the practical aspects -- more room, kitchen saves time and money, laundry means less packing, stay longer, jacuzzi, etc. Finally, I went for the jugular with the emotional appeals: "What do you remember about growing up? It's the family vacations and quality times. Don't you want to provide that to our kids? And won't that be a lot better if we use a pay-in-advance plan for the happiest place on Earth? This is what I want, don't you?"
It worked. It took awhile, but it worked. For some people, the opposite approach might work better. Starting with the emotional and moving toward the technical.