I always heard this for decades and still am not convinced the average human really thinks 199 is any different than 200. I don't know a single person who doesn't recognise it as a cheap uneffective trick
That’s not the point. Obviously everyone recognizes and knows this, but it still changes something about your impression subconsciously, even if you think it doesn’t affect you.
"..while ending‐9 prices exert a sizable impact on shopping cart additions (by nearly 20%), the impact on final purchases is marginal (by less than 4%). A possible reason could be that even if each individual product adopts its ending‐9 price, the cost of the shopping cart (which can involve multiple items) might still not preserve such a pricing structure."
This "trick" may be easier at the retail level, when the customer really doesn't know (or can be influenced) by the final total. But as the study suggests, when shopping online, we may fall for the trick initially, but have an easy enough way out to avoid making the final purchase.
Either way, that's just one form of phycological warfare that retailers use. Online shopping comes with far more opportunities to trick us compared to a brick-and-mortal shop. Always have enough buffers before confirming your order, so you aren't spending more than you need to (or buying things you don't need!).
Ungrateful peasants. If you simply use remarkable deals like this one to save $0.01 USD roughly 100 million times, you could be a millionaire. It’s called the economy, try it sometime.