it is 19,562 places (actual on April 2023).
Lets try to count,
average Telegram post is ~$50, average discord post is ~$20, forum is up to $100, media outlet is $250, for rating-reviews site is about $800, instagram is up to $100, facebook is about ~$60, reddit comms is average ~$200, Youtube release is about $1000, twitch stream is about ~$500, ticktock is average $100, and twitter post is about $150...
so if we multiply everything on everything we will get.. $6,234,850.00 per one day.
Since you have given an example of how much it should cost for a gambling site to spend on advertisement, then maybe it's better to give an example too of what gambling sites literally end up advertising on all those forums and social media platforms on the list. Maybe I'm wrong here but I don't think there's a gambling site that puts that kind of advertisement on all platforms as part of their advertisement.
Let's also add the fact that famous gambling platforms nowadays don't need too much exposure on various platforms as they are already popular. With just a partnership or exposure only on a most viewed platform, that's already enough form of advertisement as what these popular gambling sites are doing now is just to maintained the popularity and keeping it that way.