You also don't want to pay for all of your other shipping supplies, either. I pay for tape (I buy the Target or Home Depot brand) and big yellow envelopes, but I do not buy bubble wrap or bubble envelopes or packaging peanuts. Instead of bubble envelopes, I buy a huge Sam's Club box of yellow (10x13 I think) envelopes, put the item in a ziplock type bag (I reuse the ones I get from yard sales and consignment sales, so I try not to use new ones), wrap it in newspaper to soften edges if needed, seal it up and ship (if it is small and flat enough to put in an envelope. Otherwise, I use a box).
In the past few days I sold my Loving Family Camper for $24.99 (paid $4) and the vw Loving Family pink bug for $12.99 (paid $1). Instead of bubble wrap, I used grocery and Target bags. These are free, lightweight to ship, and it's good to reuse them for something! Once I am out of grocery bags, I used balled up newspaper (we get the Wall Street Journal for free thanks to moneysavingmom.com). Again, lightweight and FREE!
I also sold a Loving Family dollhouse for $22.99 (I paid $20 for the dollhouse plus people and accessories, the people and accessories are listed right now). Because I didn't have a box big enough, I made a big box out of two same-size smaller boxes (this is a trick taught to me by a postal worker!). I use Yard Sale Daddy's box cutter and made it fit (though I don't always need the box cutter to do this.
Also important to note, I try to clean things before I send them out. I'll use Clorox wipes, or my favorite tool, the Magic Eraser. The Magic Eraser can make a used, scuffed up toy look brand new. It can even take permanent marker off of a toy effortlessly. I highly suggest buying one to have around for cleaning time!
Once the items are packaged, I weigh them and head to my ebay sold page to print out labels. There will be a little icon on the right hand side of the page next to your sold item that says "Print Shipping Label." If you click on that, it will take you to a details page where you can put in the weight of the item (shipping addresses to and from should be automatically filled in). Once you've verified the information, printing your label is just a click away! After I print, I affix it to my box and schedule a pick up at www.usps.com.
You also might want to have a good place to store your boxes. If they're left lying around for too long, you run the risk of them turning into a robot!
I hope this information has been helpful. No need to spend more money than you need to on shipping supplies. Your toys and children's items will arrive safely without expensive packaging!