You will both be paying eBay fees (normally 13.5%) on the purchase price, shipping label, and any sales taxes.
The purchase prices may match.
The shipping is based on weight dimensions and destination, so those will probably vary.
And sales tax is set by the buyer's state/county/city.
If you can both handle that you are not going to match to the penny, you can set up private listings for each other.
When I set up a private listing, I use the buyer's eBay ID as the Title, but the pictures and description are completed normally.
That way it listing is hard to find, except by your buyer, but if the transaction falls through, it will be easy to change the title and make the listing public.