E-commerce Mobile App Development

I have an idea for a mobile app that I want to bring to life. This app will be focused on e-commerce and needs to be developed for both iOS and Android platforms.

Key Requirements:
- Design and develop a user-friendly mobile app with a focus on e-commerce
- Ensure the app is compatible with both iOS and Android
- Implement secure and efficient e-commerce functionalities

Ideal Skills:
- Extensive experience in mobile app development, specifically for e-commerce
- Proficient in creating apps for both iOS and Android
- Strong understanding of e-commerce requirements and security measures

Please provide your estimated cost for this project.