In my inbox, over the years, in no particular order:

From: YouTube Premium
Subject: YouTube Premium Individual plan price update
Email summary: The monthly price is increasing from $13.99 to $15.99.

From: 1Password
Subject: Important: We’re updating the cost of your subscription
Email summary: The annual price is increasing from $35.88 to $47.88.

From: GeoGuessr
Subject: Upcoming Change to Your GeoGuessr Subscription
Email summary: The monthly price is increasing from $4.99 to $6.99.

From: DreamHost
Subject: Upcoming DreamHost Price Change
Email summary: The monthly price is increasing from $13.99 to $16.99.

From: Printful
Subject: Product and shipping price updates
Email summary: Some prices and shipping rates are increasing.

The only two emails I could find that were actually honest about the price going up in the subject line, instead of obfuscating it with terms like “change” or “update,” were Apple’s and Panic’s.

The former had a subject “Your Subscription Price Increase,” and looked like this:

The latter was titled “Playdate’s price is about to go up a bit” and looked like this:

Also note both telling you what the previous price was.