Formal:
* Merci de votre intérêt. (This is the most formal and polite option.)
* Je vous remercie de votre intérêt. (This is slightly more formal than the previous option.)
Informal:
* Merci de ton intérêt. (This is used for friends or family.)
* Merci pour ton intérêt. (This is another informal option.)
* Merci pour votre intérêt. (This is a more casual way to say thanks to someone you don't know very well.)
You can also add a bit more detail to your response by saying:
* Merci de votre intérêt pour [topic or project]. (Thanks for your interest in [topic or project].)
* Je suis ravi(e) de votre intérêt pour [topic or project]. (I'm delighted by your interest in [topic or project].)
The best way to say "thanks for your interest" in French depends on your relationship with the person you're speaking to and the specific context of the situation.