There are always a lot of such cars at the airports. There are exceptions, of course, for example, if right before your flight arrives, someone got to the airport in a normal taxi. The price depends on the time of year, the cost of fuel, prices for new and used cars, the availability of credit lines and a hundred other factors. Ordinary tourists do not need all this. It is important to simply understand that any prices on blogs and forums are just a guideline. You can always check the current prices from transfer companies.
Neither I nor my friends have ever had a situation when the driver did not come to pick us up. I haven’t even heard of anyone complaining about it. Booking something while already in Montenegro can be difficult.