How to calculate budgets in SEO?

Question

Search Engine Optimization

We are looking for a contractor for promotion in the Russian Federation (40 branches), competitive topics - rolled metal.
All agencies offer different amounts for promotion from 60 thousand rubles. up to 800,000 rubles
In this regard, the question is:
1. How to calculate the approximate budget yourself?
2. Does anyone have any information on how much large federal-level companies spend on SEO (it is clear that it depends on the list of requests, competition, but still ..)

Answer 1

no way since your companies are going to do different things and in different volumes, it is logical to ask for an estimate of what and how much it will cost in their 800 thousand rubles.
Wikimart spends overwhelming millions of dollars of its investment in SEO