I got a very rough quote from a Toronto firm to do a location based app for web, iPhone and Android for approximately $370,000. I just talked to a Vancouver developer who charges $120/hr. As others have mentioned there are numerous variables, but most developers will usually be happy to do an initial free consultation to learn more about your project so that they can at least ballpark a figure to you.
What? I can't imagine spending that much money on a non-game development effort for a mobile device. What the heck does it do?
Note the "AND"'s. I suspect this isn't some simple thing - it's probably a 300K web app + 2 35K mobile apps.