25-30 keywords?
First - really? i mean..... really?
Second - You're asking what someone would charge but you've given nothing about the market that you're trying to compete in. There's a huge difference in the amount of time it would take in a niche like weight loss compared to a niche like outdoor customized gardening tools... Also you're setting a goal no one can ever promise (rank in top 3). If someone ever claims they can promise a ranking of any sort to you, laugh and walk away with your hand holding your wallet tightly.
Background info... you don't need to give up the golden goose.. just a little more than i have 2 sites, 25-30 keywords.. top 3.