How much were Atari games when they first came out?

I am curious, How much were Atari games when they first came out?

Like were they expensive or cheap compared to the price of modern games nowadays?

If you look at the ad here:

Vintage Computing and Gaming | Archive [ Retro Scan of the Week ] Atari 2600 Newspaper Ad

It appears the were retailing for $20 to $30 bucks.