Dear Sir,
The budget you have mentioned will give some less reliable work. We know what it takes to develop an app like WhatsApp, we chat etc. We have a good set of resources to use for the development of your app. Our coding standards are also proven to be very fast and robust.
We are ready to start the development of your app but would request you to kindly accept the budget we have bid for because this only give you an awesome product.
Let's get in touch.
Thanks