This is the wrong way to look at it. Your expenses prior to launch (with exception to employees and all), would be minimal (unless you're just outsourcing a ton of work). Hosting and a domain name is like nothing.
That said, until you launch, hire employees, have a cofounder, raising money, etc... no one is going to know you really exist and the "looking" professional or whatever is non-existant, nor do most early adopters really care or think that way.
The reason most people advise (including really good attorneys) to put off incorporating until you actually need it is basically to save you money and avoid having to undo, amend, or fix anything.
Hope that help better answer the question.
