For or At

[Gc]

what is the correct preposition to use?

I bought it FOR/AT half the price.

I sold it FOR/AT half the price.

[Milanya]

at a price/ for an amount of money
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con·text - The part of a text or statement that surrounds a particular word or passage and determines its meaning.

[Gc]

hi milanya! thanks for the reply.

so, i should say:

i bought it at half the price.

i sold it at half the price.

i bought it for $5.

i sold it for $5.

am i right?

how come eh? "i bought/sold it FOR half the price" has been used so many times. so you mean to say it is not grammatically corrects???? which is the better preposition to use?? i am so very confused now. please help me.

how about?

i bought it AT the grocery store AT half the price..

it sounds like there is a lot of AT's in the sentence.

and milanya, i know i am so insistent, but i have another question:

I am new ON/IN/AT Facebook.

This is the first time that I cancelled a project ON/IN/AT e-Lance. (e-Lance is an online business)

Today ON/IN Discovery Channel..

I watched it ON/IN Discovery Channel..

I read the article AT/IN/ON eHow.com.

PLEASE PLEASE HELP ME!!! thanks a alot.