Cheap to run

Easy to keep, no food or vets bills, no exercise required and no toys to buy/find/mend/throw/rescue from rivers and ponds.  A quick wipe over with a damp sponge  from time to time and they are as good as new and just as cute.  

Plus they don't bark like lunatics  at 04:15 ... yawn... zzzzz...

One small, furry, cute and noisy  woofer could be offered free to a good home tomorrow if there is a repeat performance...