No one answer here. It depends on the company and its needs.
The Super Bowl has the most eyeballs of any event in America. Ad costs are not measured in total dollars spent. The industry measure is something called Cost Per Thousand or CPM (the M is mille, the Latin for thousand). Obviously, the lower the better. A Super Bowl gets, say, 100,000,000 viewers. That 100,000 thousands. So a $3,000,000 ad is only $30 per thousand. But the ad isn’t run only once (unless you’re Apple in 1984) but will be shown over and over and over again. That reduces the CPM even farther. And it will be discussed in every paper, and every news site, and every blog, and get millions of hits online. Could it be seen 1,000,000,000 times total? Sure. That’s now down to $3 per thousand. Incredibly cheap.
So say you’re a small or new company and need to get attention fast. Do you go to a regularly scheduled show that gets 10,000,000 viewers and costs $300,000 per slot? That’s also a CPM of $30. The long-term impact is bound to be lower, though, and the long-term CPM higher. That’s why there is always so much competition for ad space for the Super Bowl and for similar high-profile, high-viewership, high-media discussion slots.
The ad situation for an established company is similar in some ways. High-profile, high-media discussion is obviously helpful for any company. But the ad isn’t there to tell you that the company exists. It’s there to a) remind you of how wonderful the product is; b) associate the product with good times and good memories; and c) prevent a rival for getting all that wonderful attention without competition. Coke and Pepsi are always competing, fiercely, for tiny slices of the beverage market. A one percentage point swing means tens of millions of new profits. You may think that everybody has decided on a cola (or a beer or a car or a delivery company or whatever is being advertised) but many people - a significant percentage - are persuadable. And people have short memories. Not advertising is death. Without those constant reminders people will drift away from products. The core buyers are never enough. And even they change over time. They move, they die, they shift tastes, they get families, their incomes vary - life is always pushing them in new directions. If the advertising isn’t there, the products will get abandoned. It’s a cycle almost impossible to get off in certain industries.
There’s more to it than a Super Bowl ad, of course. Properly done - and many firms don’t do it properly and die - a Super Bowl ad is a tiny part of an overall package of ads, promotions, marketing, charities, tie-ins, websites, videos, contests, all the million ways that companies try to reach out to you. I’m sure the overall budget for such things for Coke is in the hundreds of millions, maybe billions worldwide. Does $3 million still sound like a lot of money? It’s a drop in the bucket.
The fact that you thought of Coke as an example shows that it works. You can argue that everybody knows about Coke and that it was obvious. But they made it so by over 100 years of relentless advertising and promotion. That’s how it works and why they keep doing it.