In order to hit the current price point, I have to get them made in batches of at least 40, which can be mixed sizes. I keep common 1⅛" types in stock, so my restocking needs have a bearing on when I need to make a new batch, but at the moment I have plenty of stock.
£12.50 for the stem cap now, £10 for the headset cover in about a year from now based on previous form.