Yep i agree with your last statement 120% nothing more then a full refund anything extra is an amazing business practice.
And yes I agree that if you receive a purchase order at your place of employment with a wrong price and no in-date quote then the purchases order accounts for jack sh1t, its the same with all businesses, your nothing special.
However that has absolutely nothing to do with Ebay and Ebays policies.
Some people seem to have a hard time comprehending this.
Simple version of Ebays buying and selling policies again.
Once the buyer clicks on that 'commit to buy' the buyer is required to make payment to the seller within a reasonable time frame.
Once the buyer has paid the seller the seller has an obligation to send goods which match the item description within a reasonable time frame.
That's it, there is no quotes there is no 'oh it was the wrong price so unlucky buyer', if the seller uploads an item to ebay at a set buy it now price and the buyer commits to buying an item and pays the seller ebay expects the item to be posted. That's it, no grey areas, no excuses.
It is this way because Ebay has said it is so.
Seeing as how you seem to comprehend it in 'your business' terms, i'll apply it to those.
Your business miss quotes my business $42.98 in exchange for goods or services which should actually cost $270, however the quote has been sent in hard-copy, signed and dated. Now my business has sent your business a PO for $42.98 and expects the goods or services. Now your business realizes that it's stuffed the quote up and is refusing the goods or services. There is no law that states (there may well be, I haven't read the Australian business code of conduct) you have to give those goods or services for that quoted price, but it's simple business ethics that you honor all in-date quotes even those you stuffed up. If you don't word will soon spread that you don't honor quotes and soon you wont have anything to quote on.
Therefore, the sea-guls (the buyers), purchased the chips (the light-bars) at the advertised price and paid the seller. And according to ebay policy (which is all that matters in this case and not your irrelevant real world case) and now ebay and the sea-guls are expecting the light-bars. Plain and simple.