Mercadolibre (ML) is now the defacto price thermometer here as well as being a useful source for those hard to find widgets. However, it pays to use some detective skills so that you can go direct to the advertiser, thus saving some money.
For example, I was after an RGB splitter cable which I found advertised on ML for $469 and even though advertisers shouldn't indicate who they are, this one put LOGG Computer at the end of the description and it wasn't difficult tracking them down.
I contacted them on Facebook and they gave me a price of $375 which would be further discounted to $260 if I paid in cash. Que loco, no? Half the price.
There is good reasoning behind this, since ML charge the seller 11% commission and often force them to give free delivery, hence the higher price. Still, double the price is taking the piss.
It pays to keep your radar switched on at all times when dealing in ML, both as a seller and a buyer. For example, yesterday I bought some PC fans directly from a bloke in Quilmes because he had been savvy enough to add a .jpg with some text hardcoded in it (proper text will be picked up by the ML police as trying to let people know who you are), so I went straight to his Facebook page and took it from there.
When I sell on ML, I usually give a clue as to how people can get hold of me, so that I can avoid the commission, but algorithms are very clever today, often picking up numbers hard coded into an image, so we have to be imaginative - just like the Argentines who spend most of their time screwing each other anyway.