First off: the seller went above and beyond the call of duty here but also screwed up by not using delivery conf on all shipments and shipping with shitty USPS in the first place (which also costs more). In essence seller you ripped yourself off hardcore and caused your loss.
Ok - For future purposes, everyone shipping and selling items should follow my advice here. I am an e-bay seller and very experienced with hundreds of transactions / shipments with UPS, FedEx, USPS, and DHL.
First order of business,
USPS is a terrible value unless you are shipping light items (2-3 LBs) or envelopes. Parcel Post is a rip off, sometimes it only costs 20 cents less than priority and takes 500x longer. NEVER SHIP PARCEL POST. I'll explain why later. USPS in general is a rip off - do not ship USPS if your item is over 5 LBs at all. NEVER SHIP PARCEL POST. ALWAYS BUY DELIVERY CONF.
Drawbacks of USPS:
-Extreme disregard for your items
-Even if you write "Fragile" they will treat it like shit
-No real tracking, tracking costs extra
-Rip off (Costs more than UPS and FedEx - by A LOT)
-Annoying underpaid disgruntled staff that don't give a shit
-Costs extra for delivery confirmation and insurance (both free with UPS/FedEx)
Advantages of USPS:
-Good for cheap, light items you aren't too concerned about
-$1-3 shipping on items under 13 ozs
-Cheaper for International mailing and pretty much the only postal system used internationally because the others are so expensive
UPS / FedEx Advantages:
-Free complete tracking (shows where the item is)
-Free Delivery confirmation
-Free insurance up to $100
-Discounts on multiple items with 1 master tracking #
-WAY WAY WAY WAY cheaper than USPS. Up to 75% cheaper on shipments 5 LBs or over
-Easy claims process, if something breaks or gets lost (which usually it doesn't) they will refund you everything as long as you declared the value
UPS / Fedex Disadvantages:
-Light items may cost slightly more to ship
As you can see, USPS is a major ripoff and UPS / FedEx is the way to go on all heavy items. You would have avoided this situation completely and paid less on top of it, had an insured and tracked shipment and a perfect transaction.
Moral of the story for this thread:
Never use USPS.