Seems like your main point is you want every person posting to include their price.

However, that's up to the seller to decide.

Why NOT include a price?

One reason is because as soon as you set your price for XYZ, another individual can come along and undercut the price by $10 - $20 or more just to take away the business.

Another possible reason to not include a price is to be current with asking prices and more open to negotiation.

Some sellers are more 'professional' than others. They have a reputation to maintain if they are to continue in the 'secondary business' and part of that reputation is based on speedy delivery and personal service, not just on price.

Seller "A" may appear to always be 'high' on the price scale, but may have an outstanding reputation for delivery and service. Seller "B" may be unknown - a new individual who appears to be selling a 'hodge-podge' collection. Their reputation is unknown.

This is a long-standing issue for on-line collectors, pre-dating these Collector Forums and going back into the AOL Lighthouse Collectible posts.

I've not intended to offend anyone here - the question is welcome and will, no doubt, create some additional heat and light [eh JTA?]