Yes, but your idea of avocados and the Chinese reality are totally different.  Here, avocados do exist, but they are very small in size, maybe shaped like your idea of a pear, but smaller.  Otherwise, they do taste about the same, and run under 10 Rmb each.

Sometimes, at places like Walmart, or at some street fruit stands you can see the ones you are accustom to, but thy are expensive, upwards of 60 Rmb, maybe as much as 80 to 90 yuan each.

Now, as far as buying them on line, I really do not know, never tried it before.

Yes, Taobao. Different stores have them. Many in English. I bought ten of them , all fresh and extremely  delish!  They ship it in a Styrofoam box so no bruises. I would reccomend other fruits, like cherries as well, Cheaper and fresh.

Also a note. I dont know about the small avacodos mentioned above, but i doubt youll get them for 10 yuan. id say 15-20 per.

  I've got some in the back of the fridge you can have. Bit hairy. Smell FUNKY too, but what the heck, gimme an offer.