The reason that eBay auction announcements are allowed in the For Sale Petroliana section is that the Online Auctions, eBay section is often about third party sellers, repro warnings and complaints. Members requested it and I changed the rules several years ago to allow eBay announcements in For Sale.
At the top of the For Sale Petroliana section is says,
Each item offered here must be priced. Announcement of your eBay petroliana auctions are allowed. Other updated rules including 72 hour bumping limits also apply.
------- Please read and follow the For Sale forum Guidelines -------"
The opening price, current bid and buy-it-now price (or not) are subject to change at any moment on eBay. An opening price is required there, so the items announced always does have a price shown on eBay.
The referral ad fees from eBay for winning bids from buyers who are referred from our site are what keeps Oldgas.com in operation.