With current prices this could be a bit of a stretch. A 2 day rental from MIA with Enterprise is $140 for a compact (just checked). I’m sure you can find cheaper but probably no by much. So you are close to $160 all-in with gas and tolls.
https://i.imgur.com/uSHiZdS.png
If you are willing to risk using one of the lower tier car rental companies, you can really cut the price.
Not sure it is even the best comparison since we are talking reliability. Airlines manage overbooking very well, but flights delays and cancellations are the reliability issue.