For reference, Android household here.
There haven't been many apps we've felt compelled to buy. I think we still have like $15-$16 of the $25 credit/rebate from Google when we bought the Nexus 7 back in '12 - Titanium Backup and Beyond Pod come to mind as apps I've purchased.
Other than that, I just haven't seen much of anything I need that I'd be willing to spend even 99 cents on. Also, you can get a free paid app everyday from Amazon. I have gotten some good ones from that, but I'd never pay for them otherwise.