So people will ask all the time how much you get paid? Where you're going? How much it cost? How did you get that? And everyone's intentions are not the same.
Some people may see you doing well or on track with your goals and congratulate you and genuinely be happy for you. Or they might give you some suggestions or motivate you to get on track. Keep those people around! Some other people may not. Keep a stick between you and those people. Jealousy, envy and greed usually follow with those people and just like anything else, you want to safeguard what is yours.
Yes, they could probably figure it out but you are in no way obligated to share the details of your money with anyone. Feel comfortable saying nicely, I'm not comfortable discussing that with you if you want to. And end that conversation and move on to the next.