shouldn’t the relevant metric be whether they increase your chance of success more than the cost (equity) you sell them in return?
But in general, yes - VCs give something and it costs something, like almost everything else in life and certainly in business. It's your job as an entrepreneur to decide if that money is "worth it". Sometimes it is, sometimes it isn't. In the end, just like borrowing money, it's a tool that you have to decide on as an entrepreneur. It's a big decision, maybe one of the biggest at first, but one of many thousands of decisions you have to make every day.