1. Don't be afraid of playing around with AWS (and even spending some money). AWS is really good at refunding you if you accidentally rack up a couple grand in surprise bills. Also even if you legitimately spin up big servers to try a kubernetes cluster for a couple of days, that $20 you spent is almost certainly great bang-for-buck for the benefit of learning that experience and getting your hands dirty with AWS.
2. AWS billing is actually really good for what it is. If you've ever run any non-trivial operational system (in the real world), you would know how hard it is to collate all expenses and get them tallied up. AWS collates all billing data with ~24h lag and you can slice and splice it to your heart's content. After all it's a complicated distributed system that they've managed to build that doesn't slow down your services or otherwise get in the way!