I spent hundreds putting a SANDPIT in the back corner of our yard. And the sand has to be replenished regularly. The yard is privacy fenced and no cat in their right mind comes back there........
I feel it was money well spent and wouldn't consider it Extravagent though, the dogs love it!! Orson will hide his toys in it to find later, and Phoebe doesn't play with toys but loves to dig so she is happy too.