Unless your buyers are honest, it is unlikely you will receive payment for the items they have already received. You could try contacting them if they don't pay and see what they say. If they refuse to send payment, you could try opening an unpaid item dispute, which might force them into paying (or they get a strike against their account if they don't), but if they do pay, you risk getting a negative from them. Given the amount of money you are likely to lose on those sales, getting a negative would be worth it in my view because it's more than a few $$.

Sadly, in this day and age, you have to treat buyers as though they are all thieves. NEVER EVER send anything until you have received a cleared payment (although I think you know that now!). I know it's easy to get caught up in the moment, but at what cost to you? We're talking a couple of hundred bucks here.

To open an unpaid dispute, go to your sold section and to the right of the listing, click on more actions, then select resolve a problem. On the next screen, select that you sold an item and haven't been paid for it, then submit. That will open the case for you. If the buyer hasn't paid in exactly 4 days (clock hours, not days), go back into that section and select that they buyer hasn't paid and then you can close the case. The buyer gets a strike against their account and you get your eBay fees back. If the buyer gets 2 or more strikes, they can't buy from a lot of sellers who have blocks in place.

If you go back in to try and close the case and the no opetion isn't highlighted, check the top of that page and it will tell you the date and time you can close it. It may not get you your money, but it could stop the buyers from buying from a lot of people.

If they don't pay, I would also add them to your blocked buyer list. http://offer.ebay.com.au/ws/eBayISAPI.dll?BidderBlockLogin

If you don't already have them set up, set up other blocks to try and stop certain buyers from buying from you (serial pests that can cause you issues). Set the bocks to the extreme, so the unpaid strike block, set it to 2 in 12 months and so on. http://offer.ebay.com.au/ws/eBayISAPI.dll?BuyerBlockPreferences

I know that what has happened is your own fault, but I thought I'd help you out from potential future issues with buyers while I was here.