Both sellers offered free postage, with an estimated delivery time of today, Friday the 21st. One I paid express shipping on ($4), the other I chose the free shipping option. The seller & I both live in Sydney, so express shipping is guaranteed next day.
Both cables were posted on Tuesday, & the expressed one arrived on Wednesday, except it was a mini USB to HDMI adaptor, not a lightning cable. I emailed the seller yesterday (Thursday) to notify them of the mistake, request that they send the replacement immediately as I paid for express postage for a reason*, & asked how they would be paying for return shipping of the incorrect item if they wanted it returned. They said they would send the correct item once I had returned the adaptor, & that they would not pay for the return postage, or refund my express postage. I had some stamps lying around so I sucked that up & posted it back today.
I had the free postage cable sent to me at work, & it arrived today. It's also an HDMI adaptor instead of a lightning cable, & the return address is the same as the first seller. For a moment I thought it was my very speedy replacement for the first wrong cable, but I didn't give the first seller my work address, I had it sent to me at home. I emailed them to let them know about the second cock-up, am currently awaiting their profusely apologetic response.
* wanting my item immediately is a completely legitimate reason. If it had been right, that $4 would have totally been worth not running back to my house this morning after I got to the bus stop because I'd realised I'd left my lightning cable at home, & as I'm going out tonight I want my phone to be charged.