You're really ignorant, aren't you?
11 of the top 50 are commercial engines. The top engine, however, is free AND open-source. Time has been spent to making engines more efficient, but if you think that the creation of Chess engines is based solely on a business perspective, then you need to re-evaluate your life.
You don't even know what you're talking about, at all.
"hence I am not surprised to see a bot engulping that huge amount"? What huge amount? You clearly haven't bothered to go to the site, nevermind read anything relevant to price on it.
"You may expect them to spend as much or even much more than that." More than what? adaseb hasn't mentioned anything relating to the price and neither have I. Stop spamming.