1. Oracle licensing : You bring your own license. You can not buy a license from AWS. This can be an Oracle ULA, ELA, or perpetual licenses. The only support AWS has for AWS compute with Oracle license included is for AWS RDS. For all other, you have to BYOL. A partner can use OPN licenses for test and development. OTN licenses are only for trials of 30 days or less. Oracle on AWS licensing document is here: http://www.oracle.com/us/corporate/pricing/cloud-licensing-070579.pdf
2. The bulk of the AWS cost is composed of EC2 compute, storage (EBS and S3) and network (data transfer out). The pricing calculator above can give you an estimate of AWS cost.