Depending on your needs, there are a variety of places that are in the $500 range.
Here are three that I can recommened from experience...
About half way between Fort Meyers and West Palm Beach is Crooked Hook RV Resort near Clewiston Florida on the extreme southern tip of Lake Okeechobee. Clewiston is kind of in the middle of nowhere and the nearest mall is over an hour away, but if you're a person who likes to fish, this is heaven. In fact, one of the biggest fishing tournaments in the country is held there each year.
Crooked Hook was by far the friendliest park in which we have ever stayed. The folks welcomed you like old friends and there were activites almost every night and almost all are free. Happy hour's-cookouts-comedy nights-dances bingos-Super Bowl Party-execise room and more. Free wi-fi.
www.crookedhookrv.biz
A little further south in Sanford is the Wekiva Falls Resort. It's closer to clivilization (malls-restaurants-theaters-Disney World). A very nice facility, since the new owners renovated a couple of years ago. Be careful though, they charge for extras like cable & wi-fi, and you can't have mail delivered there (get a P.O. Box).
www.wekivafallsresort.com
On the Atlantic side, 30 miles south of Daytona, is Crystal Lake RV Park. A no frills, but clean & quiet park. Near the Kennedy Space Center, less than an hour from Disney. Charge for wi-fi. Limited 50 amp service sites.
www.crystallakervpark.com
I hope this helps. I'm sure you'll get many more suggestions for other choices.