fatbikes are rather expensive, but once you have one they are ok to own and run, few examples of my past experiences.....
in 2010 i ordered a mukluk from the USA, came in at $1500 but once the money was sorted and charges paid, it was still £1,000-£1,200.
on-one are releasing a complete fatbike for £999 this year, though its being sold as a trials bike....
my 2011 pugsley i bought last year was the first fatbike you could buy complete in the uk, previously you had to buy kits to build your own bikes...£1340 posted to my house was great, last years models are around £1200 where available.
the 2012 moonlander was £2,000 complete, again pre-ordered to secure from dealer, then a few month to wait.
tires are expensive, moonlander uses big fat larrys at £90 each, but they do last, some people have noted 3,000 miles on tires, some have lasted a weekend then got shredded
i bought 2 pairs of surly nate tires earlier this year, a cool £350 for 4 tires!
you can pick up 3.8'' tires from £40-50 now though.
tubes are £10 each, but the bikes will take 3.0 DH tubes, 29er tubes and even certain motorcycle tubes, all depending on how thick you want them.
BBs are the main thing to watch, they get covered in salty water, so a good serviceable BB will pay for itself in no time (£60+) and should be the first upgrade.
again with brakes, most use the avid BB7, cheap, can handle salt water, and they are ok enough to stop a 36+lb of bike and my fat ass.
frames are bombproof, as are the rest of standard parts, just take care of that drivetrain after each beach ride and they go forever.
never has a bike gave me more smiles and got me out the house as much as these
2014 surly straggler
2012 surly moonlander
14 badboy 14 carbon beargrease 13 jones spaceframe 14 straggler, 05 pugsley, 13 pugsley, 12 moonlander, 13 krampus x2, 13 fargo 2, 11 surly pugsley, 01 Volvo Cannondale, 01 dekerf limited, 98 cannondale caad2, 94 san andreas, 96 san andreas, 93 pace rc200 f3, 08 Ti moots rigormootis, 93 Ti merlin xlm, 09 Ti jeff jones spaceframe, 93 fat chance yo eddy (ex dave hemming), 11 salsa mukluk, 00 scott octane, 03 stumpjumper comp, 07 s-works fsr carbon, 08 revolution triad 2, 94 claud butler kylami, 96 cannondale m500, 93 townsend, 07 scott scale 30 carbon, 92 CR dogs bolx, 09 hooligan 1, 99 trek 6500, 10 badboy