That’s the whole “takes money to make money” concept. It’s a snowball where it goes really slow at first, but as you build up more and more the interest/growth really takes off. Generally cash savings/CDs are not going to make you a lot as they are very safe. Stocks can make more, but even then, on average take about 7 years to double your money. So 10k would be $20k if you put in no extra after around 7 years.