Price Check

On 29 July I put a tub of Greek yogurt into my basket at PARKnSHOP. Sixty dollars. Next to it a banner: "Buy 2 to save $21.00".

I bought one. So I paid the sixty and I collected none of the offer.

Price Check told me afterwards what that sixty dollars was. It's a ledger of Hong Kong supermarket prices, and every day it takes the Consumer Council's published feed and keeps it, so yesterday's sticker doesn't vanish the way it does in a shop.

Six days of a banner

Here's what it had on that tub. PARKnSHOP held it at fifty-five dollars from the 4th of July to the 24th. Three weeks flat. On the 25th (four days before I bought it) the sticker moved to sixty, and the banner went up beside it the same day. Both came down on the 31st. Fifty-five again.

So I do the arithmetic the banner is asking for. Two tubs at sixty, less twenty-one, works out to forty-nine fifty each. Nine days later I'm reading forty-nine dollars for the same yogurt at three chains, with nothing attached to it at all.

At its absolute best the promotion was fifty cents worse than patience. Fifty cents.

The banner wasn't lying. Buy two and you do save twenty-one dollars off sixty. The sixty is the part it doesn't mention, and the sixty is the whole manoeuvre. What was the banner? A five-dollar rise wearing a twenty-one-dollar sign.

I've got the same episode sitting earlier in the record. Late June. Identical jump to sixty, identical banner, identical drop back afterwards, and the whole move ran twice inside forty-one days.

None of that is visible from a shelf. You get today's sticker and today's banner and nothing else. I can see it because I'm holding forty-one days of prices across 2,680 products, and I only collected eleven of those days myself: the other thirty I recovered from the government's public archive of the same feed, in one pass. My history is older than the tool holding it.

What the walking is worth

There's a second half and it's the modest one. The same prices plan me a walking route. Across all forty-one days, buying my eight-item list at the cheapest chains against the dearest tops out under thirty dollars, and on the flattest day it's under ten. Today it's ten ninety on a basket of three hundred and eighty-two. Under three percent.

I told it not to add a second shop for less than twenty dollars. It sends me to two shops on all forty-one days anyway, and not once for the money. No chain on my list carries everything. PARKnSHOP has seven of the eight items and the eggs only turn up at Wellcome and Market Place. It goes for the eggs.

Nothing else I've built touches this one. It's a household ledger.

Where the two scores disagreed

One shopping trip has gone through it so far. Eight lines, the 29th of July, the yogurt among them. The ledger scored that line twice and the two scores disagreed: one read it as a good shop, the other as a bad week. It printed both and left them sitting there. I read the run of prices afterwards and the bad-week half was the true one.

The money was in the yogurt. I've got the days now and I'm keeping them.