Nice build, 2 arduinos (one on the weather station, another on the receiver end of a wireless RF to display data). This could be expanded too for other systems to use, and as one commentor added, other weather stuff added to it. I think the total cost is around $40 in parts. Another comment mentioned using an atiny for the transmitter too that would be a bit cheaper and consume less power.
http://www.instructables.com/id/SOLAR-POWERED-ARDUINO-WEATHER-STATION/