Interesting about about 2k, to give a nice round number.
Voyagers is estimated to have insufficient power for communication by 2032, so from its launch we'll get a rounded 60 year battery life. Fairphone doesn't have plutonium batteries (though that would be pretty cool) but you can replace batteries. Let's say you replace the battery every 2 years which means you need 30 batteries. At 40€ a piece the cost of batteries is 1200€(and you get one extra battery with the phone). Add in the cost of the phone with the delivery of phone + 30 batteries and it comes out to about 2k.