[wtetzner]

The cost isn't in starting the debugger, it's getting into what you think is the right point in the execution of the program, and then stepping through one step at a time until you notice something is off.

With printf debugging, you can put print statements everywhere you think something might be wrong, run the program, and quickly scan through the log to see if anything doesn't match your expectations.

[Too]

Most debuggers have conditional breakpoints and print-breakpoints, no need to step through line by line manually. If something strange happens just right-click and insert a print as the program is running.

With print-debugging if you find a bug you have to stop your app, insert print lines, recompile, redeploy, relaunch, click through your app to reach buggy location and then scan through log. This really feels like stone-age once you've ever used a IDE.