There's a $300 charge for getting a plate for the first time. This has been on the books for about 15 years, but there have been good budget years when the state has waived this charge. I don't remember paying this for vehicle #1 in 1998 when we moved down here, (only brought one car down) but we definitely paid it when we went to having a second vehicle at the same time in 2001.
And that's before you pay for the plate itself, which as SWGB has said, is based on size/weight of the vehicle.
The nice thing for long-time residents is that once you get the plate, you don't have to pay the $300 again if you sell a car and then move the old plate to a new vehicle; you just keep paying the annual renewal fee (adjusted for different vehicle size as need be)