I just did some looking at my super-duper spreadsheet. If I add up all the credits I have gotten and the postage costs - it comes out to $2.49 per credit. (each credit costs $2.49 in postage).

If I add in the "free" books I have sent from my posts in the bazzar, the postage rate goes down to $1.43 per book.

Either way, I think it is still less expensive for me since if you buy multiple books from one vendor on another popular (un-named) website the average cost is $3.23 per book.
Also I don't have to lug all those books to the Viet Nam Vets thrift shop.

Soooo, I guess I'm saving money (I didn't figure the cost of mailing materials or the trip to the post office as any good cost accountant would), nor can I figure any way of factoring in the sheer fun of doing all this.

I donate 10% of my credits earned to "friends of PBS" whenever it comes out even - I wonder how much of a tax credit I could take (as if that would ever make a difference!)

How much do you figure you are saving? Just what do you figure a credit is worth.

wc

$3, not using your accounting strategy, but that is the total actual cost of the average book I mail out, with DC and PBS postage fees.  I only buy tape as almost all of the books can be wrapped in the printed mailing label (I do put hardbacks in envelopes).  I don't have to factor in any gas because I can drop them in any mailbox since I use PBS postage.  I am quite content paying $3 for a book.  I went to B&N the other day and bought 6 bargain books (hardbacks) and spent $41 after my member savings.  That is still almost $7 a book...and I used gas to get there :-)

I think PBS is the best deal in town, and we get the added bonus of meeting other people that share our love of books

Well, according to PBS, I have saved hundreds of dollars. I have no idea how that is calculated or in what universe I have saved money -- but that's the figure I point to when my spouse grouses about how much money I spend on books.

Honestly, I don't know that I've saved any money overall, but that's not really what I'm here for. I like books, I like to trade books, and I like getting mail. I'm here purely for the entertainment value. Though, I'm sure I have saved money on a few very nice wishlist books that I would have otherwise had to pay full price for. 

or in what universe I have saved money

Yeah, I went to Publix the other day for Cat Food and Ice Cream - checked out and gave them $45 (ice cream is expensive?). The receipt said I had "Saved $8.32" - someday I'm going to go to the service desk and ask them to transfer that to the phone company for me.

The "Joy Factor" of PBS is hard to figure. I'm happy with assuming I spend $2.49 per book. Even though I may be deceiving myself. It's a whole lot cheaper than going to the movies.

wc

Like Wayne, I have a spreadsheet which is like a outgoing transaction archive, but with costs.

I basically try to calculate my cost per credit, which is usually postage plus cost of book (if I bought it for the purpose of swapping) averaged out over all my outgoing requests and deals offered. I also don't factor in mailing supplies which are mostly recycled (= free) except for packing tape, the paper/ink it costs to print labels, my time, or  theoretically how much I pay to "store" my books in my house. I walk the packages to the post office or a blue box.

I have no idea how that is calculated or in what universe I have saved money

PBS assumes that the average cost of a used book is $4.50 and the average cost of mailing a book is $2.38 (the 1lb media mail price).

The different between the two is $2.12.  Savings is 2.12 x however many books you have received (officially.)

Edited: this is how the "Member savings" at the top are calculated. I think PBS uses some other data about how much a used copy of a given title costs.

Of course, this doesn't take into account your packaging, gas, or time costs, or the fact that (a) you could have found the book for less than $4.50 or (b) you might not have wanted to buy that used book at $4.50

The best way to save even more money on PBS is to offer deals of more than one credit. Your average shipping cost goes down dramatically for each credit that you get.

It is counter-intuitive for some people, but the best way to save $ on PBS is to offer books for free. (not in single-credit deals, however. I think of those as RAOKs, because they actually cost you money to offer to people.).

I've never been overly keen with math, so I've never done the calculations some of you have done.  I don't think my per credit costs are as low as some of you, but I do know I'm saving a TON of money over purchasing my books elsewhere. 

Wayne, I think it's great that you seem to be having such a blast with the site :)  I've watched your posts lately, and all I can say is I wish we had more members as interested and thorough as you!  It's cool that you donate your credits back to the Swap, but don't forget that there are more places to send your credits than just the Friends of PBS - like the Military Donation Program.  They've received a LOT of help from many members, but they haven't reached their goal yet.  Not only would you still be contributing to an extremely worthy cause, but you'd get a set of groovy wings to go with your silver credit icon.