My time is more valuable than the caller's time so there is no way I can make it more unprofitable for the spammer than it costs me in my time.
My technique for spam calls is to waste as much of their time as possible while minimizing the amount of time it costs me - I answer the phone, put it on "speaker," and don't respond. Most of the time it is a robocall so I let the message play to the end. Often the message is "press 1 for..." I press 0 which sometimes gets an "operator" on the line and bypasses number mazes. If it does not, I press 1 (or whatever) which generally gets a human on the line. I then let the human play the "hello" "Hello" "HELLO, is anybody out there" game until they give up and hang up. Quite often it wastes several minutes of the scammer's time.
The beauty of this technique is that it takes almost none of my time since I can go back to working while the scammer is playing the "is anyone out there" game.
Prosecution and lawsuits could make it unprofitable.
Jail time would make it very unprofitable.
For example: