I'm still familiarizing myself with the site, but I am wondering why books have $ plus credit listed to purchase? For example:

For example, You Slay Me (Aisling Grey Guardian Series): PBS Market Price: $8.09 or $4.19+1 Credit.

I had thought that the swapping was free, i.e., we can turn "credits" into books without using $$. What is the $ used for? Do we need to post $$ as well when posting our list? Does it go the sender or to PBS? (When I posted my first book I don't recall seeing anything).

Thank you for any clarification. 

We have the opportunity to do both.

The PBS Market has books you can buy for cash or cash plus credits.

Most of the books swapped on this site are swapped one person to another for credits.

There is no need at all to buy a book, it is just an option for some books.

For more information browse the Help Center.  It can explain most everything better than I can.

That price + credit is if you buy it directly from PBS. Since this book has an order button, that means you can get it from another member for just one credit and you don't need to buy it from PBS. If you wanted a new copy, you could use the Buy It New button, but if you are okay with a used copy, use the Order This Book button.

PBS Market Price: $8.09 or $4.19+1 Credit

The answer is in what you posted.  The hello highlight (added by me) indicates that you may purchase the book directly.  Either pay full price, or pay a reduced price plus a credit.

You've only been a member for a few hours, read the articles in the "Help Center".  The "Help Center" is a GREAT resource.  There is a lot of information there.  The "Help Center" is located at the top of every page, just beneath the center of the blue bar.

I had thought that the swapping was free, i.e., we can turn "credits" into books without using $$. What is the $ used for? Do we need to post $$ as well when posting our list? Does it go the sender or to PBS? (When I posted my first book I don't recall seeing anything).

You were correct. All members offer books for credits, and that is the "currency" of this site. You can use the "Order This Book" button to order the book from another member for 1 credit.

In addition to the member trades, PBS itself offers a "PBS Market" where you can purchase, either for money or some combination of money and credits, New (or overstock, or remainders) books. Those are being purchased from PBS, not another member. You use the "Buy This New" button to purchase books from PBS.

Either button can be missing from a book listing, in the first case, it means that there are no copies available to order from another member, and in the second case, it means that PBS does not offer the book for sale.

Others have answered your question well ... I just want to say "Welcome to PBS" buffy.  I hope you enjoy the site as much as I do.  It's great you've already discovered the Forums; as you see, they are quite dynamic and members are always willing to help new people orient to PBS.

Thank you, everyone! Now I get it. I am glad to be here; I want books to find good homes. Just mailed my first book, and look forward to ordering my first one. 

This is what I've posted for my own new members:

PBS is a book swapping site. Books will have either an "Order This Book" button or a "+ Wish List" button, depending on if the book is available or has a waiting list. The Book Browser under Search will let us select to search only for posted books.

That said, two ways to buy books have been added over time. PBS earns money from these sales. These are bookstores that give PBS a percentage on sales; they are not PBS. This helps pay for our server time and other expenses, keeping PBS from having to charge any membership fees.

One is the PBS Market. This is actually several bookstores. There is a banner ad for these books on the Home page. They are the books that have the "Buy This New" button, with two prices. The lower price includes a credit. These books are color coded as green boxes under the Author page.

There is also a button to buy books from Amazon. This is on the book detail page. There may be a Kindle button as well. There is also an "A" in the top banner of every page. Using this button to enter Amazon will credit PBS with a percentage of the sale, even for items other than books.

These folks have already answered your questions better than I could have, but I wanted to bid you welcome.