They are repairable, quite easily, if funds are tight or time is of the essense.
Even thought these switches are only $16 (GBP 9) to buy a replacement, if you don't do the side stand mod you will most likely have to replace the switch again and again (see below).
Remove switch from side of bike and cut off cable ties and unplug from wiring loom.
Scratch off that black silicone plastic-like sh!t from the back of the switch.
Remove the two small phillips head screws (lazy ar$e factory monkeys may have only fitted one) that hold the cover on.
Lift off cover.
There, you now have all the innards exposed that you can clean. Don't loose any springy bits.
Got a phone? photo innards before you pull apart to help with reassembly.
Remove the brass contact bits and polish the muck off them between your thumb and fore-finger.
Refit the bits and give the innards a short spray with electrical contact cleaner/lubricant.http://www.supercheapauto.com.au/online-store/products/CRC-Automotive-Electronic-Cleaner-300g.aspx?pid=13177#Cross
Reverse the disassembly and refit cover, screws, and seal with some bathroom silicone sealant.
Next, remove the side stand and in a vice, ever so slightly bend the small tab that pushes the plunger on your switch, so that the switch plunger is pushed in an extra couple of mm when the side stand is up.
The switch has been badly designed and only just makes the contacts close. This causes small electrical arcing on the brass contacts resulting in early switch failure. By having the plunger push in further this won't occur again.
Refit switch and stand to bike and then cable tie wire to frame and reconnect to wiring loom.
Cost = $0.00 (if you already have some elecrical contact cleaner and silicone sealant)
Time = half an hour