Uber charges you for returned lost items, so don't over reward

I left an item in an Uber. I received it back a few hours later through the Uber system contacting the driver and the driver coming round. I gave him a handsmoe reward. HOWEVER I was not impressed when Uber then charged me R90 as well for the driver's trouble. This charge is o-where mentioned on their website. I would obviously have reduced the reward if I had known.