How to write a business proposal for a company?

Question

Web development

Interested in how to write to a company to which you want to make an offer for product development?
What should be written about, what should be indicated, what should not? Anyone with similar experience please share.
The software is aimed at automating some processes, possibly increasing customers/sales, and reducing some costs.
And as for the cost, how to calculate it and how to talk about it?
Thanks in advance for your replies,

Answer 1

Duck and write, directly, that we offer such a product, it optimizes such and such a process, which will increase sales by up to 10% and reduce costs by 8%. Explain what will benefit the client. Do a little analysis yourself of how profitable it is for your client and tell us about it.
I estimate the cost by evaluating my labor costs and the average price in the market. When I don’t know the average price, I analyze it, find out from competitors and partners for how much they are ready to perform such work.