All new domains are sandboxed. A 5 day old site doesn't have any kind of track record for how your clicks perform for the advertisers. Google makes no money from PSA's, so they are shown when there are no advertisers for your content or there is a stop word. Different niches pay different amounts and a penny a click is not that uncommon for many niches. Where your traffic is coming from also affects payouts - and some of those clicks may have been deemed invalid (again, google doesn't get paid for those). Yeah, google paid you 40 cents instead of $4.00 because they wanted to cheat you - perhaps because they needed the money. Right! If adsense isn't working for you, try another network.