Main Entry: upsell
Part of Speech: verb
Definition: to try to persuade a customer to buy a more expensive item or to buy a related additional product at a discount

No Portuguese from me right now, like I said, my brain just died... : )

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Note added at 5 mins (2005-10-04 22:52:16 GMT)
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I meant to say, maybe with this explanation, maybe someone can come up with a Portuguese equivalent?

Eu diria assim.

[PDF] PT- Multimédia – Serviços de Telecomunicações e Multimédia, SGPS, SAFile Format: PDF/Adobe Acrobat - View as HTML
número de subscritores de serviços da TV Cabo, essencialmente através duma estratégia de upselling. bem sucedida. Esta performance é assinalável, ...
www.ptmultimedia.pt/pdfs/Res-PTMM-1Q03-POR.pdf

As an isolated word/terminology can be a little hard to determine the best target equivalent. If "upselling" here means "selling at a price that is above the market average price it may even be possible to apply the BP term "super faturamento". If it refers to selling quantatively more than expected, then you will be dealing with the second option "indice acima do esperado" ou "acima do indice esperado." Obviously, the context should clarify which would be the best option, or even give a third option.

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Note added at 3 hrs 30 mins (2005-10-05 02:16:48 GMT)
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It seems, however, that you talk about sales strategy which would be "trying to sell at the highest price as possible" in that case "venda verticalizada"