Offers vs messages: what's the difference?
Messages are for chatting; offers are money decisions. They're kept separate on purpose.
This trips people up, so here's the simple version.
Messages = your mailbox. Just for talking with a person — questions, details, a friendly hello. Saying "I love this!" in Messages does not commit you to anything.
Offers = a money decision, in Activity. When you actually want to suggest a price, you use Make an offer on the crystal's page, and it's tracked in Activity → Offers.
Why separate? So a friendly chat is never mistaken for a real offer, and a real offer never gets lost in a conversation. Talking and buying stay clearly apart.
Quick guide: Want to ask a question? → Messages. Want to suggest a price? → Make an offer.