Actually, if a change like this is introduced on eBay.ca, it may be a problem for sellers who list a lot of items in multiples (not multi-variation listings, but the same item in quantities).
GTC provides inventory tracking; if the listing is ended or re-listed as "sell similar" as 30-day (or other fixed duration) the automatic tracking of available number of items disappears and you have to keep track manually for each item. Sometimes an item will take quite some time to attract that first buyer, especially if a seller has a lot of multi-quantity items.
I suppose the alternative would be to end a stagnant GTC listing before the 18-month deadline and list using "sell similar" as GTC again to avoid the surcharge.
Many Chinese eBay sellers list this way (GTC with quantity items) in selling cheap manufactured items. Maybe this is just eBay's way of looking for extra fee income, since I'm sure many of those sellers won't want to have to closely monitor every one of their thousands of listings.
I have no doubt this surcharge will come to eBay.ca sooner or later.
