An RCS Rich message is the cheaper of the two types every US RCS message is billed as. It contains only text, plus any mix of reply buttons, a call button and links that open the phone's browser.
What keeps a message Rich
Text of any length, emoji, up to eleven reply buttons, a Dial button and an Open URL button that opens the normal browser. The words on the buttons are not counted. Anything else, a card, a file, or a map, calendar or in-app browser button, makes it a Rich Media message.
How it is billed
Per 160-byte segment of text, the same way inbound and outbound. On SimplyRCS that is $0.0039 a segment, plus the carrier's Rich surcharge at cost. The phone still shows one message however many segments it is billed as. Every element is sorted into its type on How RCS billing works.