For communications that aren’t really project related:
Try to respond without inviting a long discussion.
Respond with an acknowledgement and something positive. If you have seen it, say so, and make a short statement about it.
This hypothetical person only said it’s great, so match the length (one to a few words). If you haven’t, say something about checking it out/looking at it later (and thank them for the info).
If you feel the conversation is getting too detailed and time consuming, slowly scale back your responses to simpler and shorter replies, while still being pleasant and professional. This will help to slow down an unmanageable conversation.
The key is to respond without starting a discussion, unless you would like to have one. Your hypothetical person there is unlikely to want an in depth conversation anyway. That sounds to me like someone who just wants to feel involved in their project. They want to feel useful, and once they do, they may contact you a little less.
Responding will always require some attention, but you can be polite and positive without necessarily taking up a large amount of time. If you have multiple Buyers at the same time that communicate a lot, try to choose a time when you can stop and respond to each of their messages at the same time each day.
If you are worried about too much time being spent on even short personalized replies, you might consider keeping a few notes on mildly interesting topics (related to your work) that you can cover with a minimum of writing, and have it ready to choose from in case your Buyer really wants a conversation.
Also remember that these are your Buyers. You can respond nicely and professionally without treating each one as if they’re a long-lost friend. But if all else fails, make sure to reply with something pleasant, rather than nothing at all.