Not sure how it is for Miami, but for Lake of the Ozarks (who saw over 13 million visitors this year) they do this daily. This is their bread and butter and they do very well at it. They hardly have any agency packages, it's all local restaurants, salons, events, stores...etc. Ad rates may be lower than Miami, but the market concept is the same. Maybe Miami needs to bring their ads rates back to reality?
Ad rates are based on actual listening levels. A station in Camden, AR, might cover 50,000 people while one in Miami might cover 5,000,000 people. So the Arkansas station might cume 5,000 in the annual county by county Nielsen survey, the one in Miami cumes a half a million or more.
I'll betcha' that the local newspaper... I find one that is a daily in Camdenton... does not charge as much for its 5,000 circulation as the 100,000 that the Miami Herald has, either.
The fact is that in large metro areas, single location businesses are pretty much unable to use mass media like radio, TV and daily papers because their customer base is a tiny part of the metro area but the ad media charge for full market coverage.
I doubt the Lake of the Ozarks region saw that many visitors this year... not tourist based area has done well for the last eight months.
Oh, and in tiny markets like that where stations are owner operated, many of the restaurant ads are trade for the owner to use, not cash deals. Many, many small owner operated stations appear to be unprofitable. But the owner takes a salary and trades everything from their heater/AC unit to their car and their home maintenance. But the business model changes in larger markets where businessmen are more sophisticated and analytical and in many cases use local ad agencies for their campaigns.
And one of my first jobs was summers at WCCW in Traverse City, MI... another tourist based economy. There was very little advertising from tourist attractions because merchants knew... and that was 60 years ago so it is not new news... that tourists did not spend a lot of time listening to local radio stations while on vacation.