You can opt out of simple delivery in some cases, eg a buy now for £20 or less can be sold via ‘simple delivery’ or the classic ‘custom delivery’ where you specify the details
There have been many changes to the way that fees etc are charged, including the combination of PayPal fees into eBay fees, resulting in a net reduction previously there were offers such as 80% fee reduction, but taking into account buyers fees today vs sellers fees previously my trend is lower percentages of the sale going to fees
(I am then happier more often to use a eBay ‘promotions’ and to pay an extra fee for wider advertising)
Buyers look at the bottom line, and will pay up to an overall total.
If your item is listed at £20 or below for buy now you can set a lower postage rate as appropriate rather than the set £2.70 large letter (and have the option of calling it free post)
The EBay simple post option is similar to Vinted, with the exception of sellers not getting stung by RM actual costs
For parcels it can work out a bit better, as when it comes to producing the label it is possible to produce a label for an ‘upgraded’ heavier parcel
without taking the hit
As always with eBay and Vinted it ultimately comes down to whether or not an item is viable to sell
It does frustrate a little when a buyer takes multiple items and they are all processed separately, I recently had a sale of 4 items - all in separate packages, two by RM and two by Evri. Previously I could have combined postage and part refunded if they had paid the full amount, or if I had shown as ‘free post’ I would have have made more £ on the sales