The problem isn't the people paying to get in the boats, it's the people sending them and taking the money.
(We'll leave the French, for various reasons, turning a blind eye for another day.)
I'll try and explain the Australian version of turning the boats back.
Before; all the boat people, those who had paid a lot of money to traffickers and didn't actually drown by accident or design, got picked up, taken to safety, got given a refugee visa.
The Traffickers could sell this...not only will they pick you up, take you to the mainland, they'll give you refugee status.
Now; those people who have the money keep it in their pocket because they want to go to Australia, not some off shore 3rd party destination and you Don't get refugee status.
The Traffickers can't sell this - its not what the customers want.
No demand - No supply.
Very few boats, usually a few un orginised private individuals - who still get picked up, taken to safety and mostly don't drown.