Do you advise me to buy .mobi domains. Price is too high, Is it really worth?

If you have mobile only site to promote thru dot mobi directories, but entering mobi from phone numeric keyboard will take much more efforts than com.
dot mobi will cost less now than dot com name. godaddy prices for example dot com - $9.99, dot mobi $7.99.
I was thinking dor mobi for my mobile only product a year ago but now confident to buy dot com name.

mobi is still up in the air.

If you have the website, the content of which concerns mobile phones, it is better to buy .mobi extension. Enom.com, directi.com and godaddy.com register them at a low price.

Well if you are doing a mobile version of a site I would use http://m.domain.com as that is fairly standard now. Maybe if it is a completely mobile application that needs no regular portion to it.