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.