Live transcoding pricing calculations are simple things. There are 3 types of profiles are available.
SD profiles charge 12.5 USD
HD profiles charge 25 USD
UHD profiles charges 50 USD
For finding the difference between these 3 profiles, you simply check the mentioned URLs
You can choose these profiles based on your encoding Bitrate. The encoding video resolution does not matter to select the profiles.
Based on your bitrate, you can choose a combination of these profiles. For example, You are encoding the stream at 5mbps bitrate. So you 4 Mbps(Bitrate>3, so HD),2 Mbps, and 1 Mbps output including source. In this situation, you need 1*HD and 2*SD profiles.
1*HD = 25USD
2*SD = 12.5 USD + 12.5 USD = 25USD
So a total of 50 USD per month you need to pay. Also note that 50k Video Transcoding & Recording Minutes charges 20 USD.