黐線 chi1 sin3 – crazy, idiot; nuts
ParknShop were selling this cheese for HK$40 (which is reasonable by Hong Kong supermarket standards). Then a few weeks later it went up to HK$88, which is definitely 黐線 chisin. Then it went back down to HK$44.
Then it was HK$22, which is slightly cheaper than the regular price in the UK (£2.55, since you asked). Only in some PnS stores – one branch of Taste is selling it for around HK$70.
But there was no information about those earlier prices. This from a company that will advertise reductions such as HK$88 down to HK$87.90, not to mention “alt fact” reductions (where the higher price might have been charged for one day, if at all).
Sadly, it’s not one of my favourite Waitrose cheeses. OK on toast, but that’s all.