I think £3 for coffee is ridiculous and don't pay it if I can help it. I just get the same thing from McDonalds or Greggs for half that amount. I try not to pay for water either and will take tap water. That's also due to plastic waste, but the prices some places charge is often just terrible value for money.
Supermarkets sell small bottles of water in multipacks for about 6 for £1, but service stations, pubs etc often charge about £2 for one small bottle.
I will also avoid paying more than a pound or two for parking if I can do so safely and without causing annoyance for others by parking on narrow roads etc. But sometimes if you want to go to a particular place, paying for parking is unavoidable and other forms of transport often impractical.
I will pay what is a reasonable price to me, but most things are often piss taking prices. You also have to think about how much such things add up to per year if you do them a lot. Unless you have a lot of spare money, you will almost certainly have to do without elsewhere due to such spending.
Taking the DH who has two large costas a day, say these are £3 each and just every working day, that's £30 a week, £130 per month or over £1500 per year just on coffee. If that sort of spending meant that I couldn't afford a holiday for example, I would hope that he could cut the coffee down significantly, and take it from home in a travel cup, for a fraction of the price.