There are several preconditions, including operator training, certification, and TSA pre-screening, which are not included in the $5 fee. Plus, you would likely need to get an attorney specializing in aeronautic regulation (and who understands the legal difference between total takeoff weight and payload weight) to file your paperwork. Plus there will probably be periodic inspections, although they did say they won't require takeoff checklists like on regular aircraft. Plus, if you make any changes to the drone (such as adding anything like a battery which changes the weight) you may have to do the whole process over again. All of that stuff costs money.
It was a huge mistake to set the threshold weight at 250 grams. It's like asking people to get a radio operator license to carry a cell phone.