I think it's a matter of expectations. When I go to a restaurant, I'm OK knowing the price is X, but today (or right now due to whatever) the price is lower, but I don't want the "surprise" the price is X+Y when it's usually X due to something, e.g., shortage, high demand, or time of day.
If restaurants want to have time of day based pricing, I'd be OK with the base price being the highest price, with discounts during other parts of the day. For example, early bird specials have always been a thing (lower prices late in the afternoon before the evening rush). What I find objectionable is there being an unknown, unexpected, up charge based on anything, time of day, day of the week, phase of the moon, ... It's objectionable even when the up charge is mentioned when I arrive due to the overhead of having to go somewhere else.
Yeah, I guess eventually we'd become conditioned to expecting cheaper food/services at certain hours, and congestion charging at other hours. Maybe we'd even become accustomed to some vendors having large variance and other having small/no variance. I would be OK with there being a large variance as long as the average price seems reasonable.
Fast food restaurants should instead have something called "rage pricing" instead of "surge pricing".
Rage pricing would be for them to randomly post on social media that cheeseburgers are 50 cents tomorrow. There would be a special line where people can order ONLY off the rage menu which would be sodas and the one special. The way it would work would be a dedicated cook for the special that just makes cheeseburgers whether they are ordered or not - no customizations on the rage items.
At least here in Michigan, bars & restaurants have been offering "Happy Hour" specials (at times when business is typically slow) since (vaguely recalled hearsay) the 1930's. I've never heard anyone complain about that practice.
Similar for discount coupons, "3 Day Only" sales, "end of season" sales, loyalty cards, "Senior day", etc., etc.
The problem for Wendy's is that their new CEO suffered a very public hoof-in-mouth brain seizure. Imagine if he'd announced that every Wendy's location would be open on Sundays with "we'll be showing God who's really the boss!".
If restaurants want to have time of day based pricing, I'd be OK with the base price being the highest price, with discounts during other parts of the day. For example, early bird specials have always been a thing (lower prices late in the afternoon before the evening rush). What I find objectionable is there being an unknown, unexpected, up charge based on anything, time of day, day of the week, phase of the moon, ... It's objectionable even when the up charge is mentioned when I arrive due to the overhead of having to go somewhere else.