Once your datalink equipment is installed and working, there is also the price of the actual information. Because Bendix/King created its datalink system in cooperation with the FAA, it offers the basic text data of metars, forecasts and pilot reports for free. But starting soon you will be charged a flat fee of $49.95 per month to receive graphical information such as the Nexrad radar pictures.
With its request-reply system, Garmin charges by the request. Actually, it is Echo Flight, the provider of the information, that charges to supply the data to your Garmin receiver. The price for an unlimited number of requests is $600 per year. If you expect to request no more than three radar images, metars or graphical metars in any flight hour, the cost is $335 per year, with a one dollar charge for any request above three during a flight hour. Or you can simply be charged one dollar per request with no fixed annual or quarterly fee.
Neither of the two technologies used to get weather into our cockpits is a slam dunk winner over the other. The advantages of each are clear, but there is no way that either can eliminate its fundamental shortcomings, or have its advantages overcome by the other in the future. If you're already in the Garmin camp with a 530 or 430 in your panel, the GDL 49 satellite receiver holds enormous advantages in cost and installation simplicity over the Bendix/King system. If you already have a Bendix/King multifunction display installed, the advantage in cost and complexity goes to that company. If you're starting from scratch, the costs are nearly the same because you need to install a Garmin 530 or 430 plus the satellite receiver. But then you get so much more capability from the 530 and 430 with their comm transceivers, and VOR/ILS receivers, as well as a fabulous GPS navigator, that it's hard to compare the two systems in that manner.
Not since the 1950s when the country was trying to decide between VOR and tacan as the foundation for navigation, and between UHF and VHF for communications, has there been such a stark divergence in avionics technology. The military went with UHF and tacan for specific advantages, while the civilian world opted for the less complex VOR and VHF systems. I think we have the same situation now with datalink weather, where both technologies will exist in parallel, each retaining its own advantages but unable to eliminate its disadvantages. All that's left for pilots is to pay your money and make your choice. And you will love having weather in the cockpit, no matter what path it takes to get there.