Is it a pint?

As infuriating as it may be, it's a good occasion to learn to let go.

Rationally, you're paying way more than the liquid in the glass, so just mentally tell yourself that the haircut is included in the price, and that's fine. If you can't stand the price anyway, change bar.

You're there to chill. Just chill.

I think your expected outcome is actually the desired one, to kill shrinkflation in favor of actual price increases. When the measures are all the same you can compare apples to apples across different businesses.

The way they got to the 25/ 35 split involves even more craziness. In England the law said spirits are always measured in sixths of a gill. This entire unit is obsolete, but 1/6 is a tiny bit less than 25ml. Fine.

However in Scotland two sizes were common, a fifth of a gill (slightly more generous than England) and a "nip" or quarter of a gill (a lot more generous). If you're used to ordering a "nip" of something and now you get a lot less you'd be very angry! So the 35ml option is there for the kind of Scottish or Irish establishment which would have been used to these larger measures rather than either try to keep the gill (which is a stupid unit nobody else needs) or anger drunk people.

I wouldn't be surprised if the "Make a sign" difference was to allow licensed premises to gradually shift to the more profitable, smaller, size. Maybe you change the place you own in Glasgow to 25ml first, and if the locals don't kick off you can try Aberdeen next, otherwise try again in a few years.

When CAMRA was new in the early 1970s, they started a campaign for oversize glasses holding a pint to the line instead of a pint to the rim, so that there would be space for a pint of liquid and a head in the glass. The big breweries hated this idea and mounted a reactionary campaign arguing things like it would be too expensive to replace all the glasses, or serve customers the full measure they had paid for. (My father was a new recruit at Guinness and sadly one of his early tasks was the pint-to-brim campaign.)

I enjoyed reading this site and appreciate the passion and the effort.

The "loss of the pint" is basically shrink-flation. When a bar's costs and/or overhead goes up, they must do some combination of cutting expenses and raising prices. Raising prices means either selling the same stuff in the same quantity for more, or selling cheaper stuff OR less of the same stuff at the same price. Most bars will opt for the latter options to avoid raising prices, because raising prices is more likely to create complaints. All caveats apply, of course -- drop portions or quality too much or too often and you'll get complaints for sure, but "within reason" it's the lesser of two evils.

This is why I personally don't feel like I'm being cheated out of 2oz when I buy a $8 14oz shaker pint of IPA. Clearly, the cost per oz at this bar is $0.57. A 16oz glass would cost $9.14. They don't owe me the 2oz for free just because they used the word "pint". If the state government started enforcing pint measures again, bars would just drop the word "pint" from their signs and menus.