I’m for having good website translations, but you are asking for way too much money.
a) you’re not a professional translator
b) the texts to be translated are not really complicated
It is not true that the average value of other submitted proposal is $2000. You looked only at the Polish and the Hindi proposals, but there were other proposals before. Checking what has been proposed before is a good idea, but you can’t follow overpriced proposals (both the Hindi and the Polish proposals are probably going to be rejected for being to expensive).
As for the link with average hourly pays, you can’t justify your prices with it. Translators are paid per words (sometimes per characters), not on a hourly basis. The hourly pay you see on the website you linked is based on what a decent translator can translate / hour, which is about 200 words. Translation rates depend on the text’s difficulty and character and on the translator’s experience, but the average price for a normal text is $0.1/word. Hence the hourly rate of ≈ $20 of the website you linked.
If you want to translate the website, I’d advise you the chose a rate / word and explain why you chose this rate.
The following guide could help you to prepare a better proposal.