[eric_bullington]

> You're also most likely going to pay per word, so if you can figure out a good way to not send them sentences you've already had translated you can save some money

The typical process would be to send them the translated sentences in Trados or tmx format (translation memory) and ask for a discount for 100% matches (you may even be able to discounts for "fuzzy", or <100%, matches). These discounts are often referred to as "Trados" discounts. That said, not all agencies/translators offer such discounts.

> We once caught a translator (NOT of the above-mentioned companies) located somewhere in Europe inserting some choice political statements about a specific biotech/GMO company we had as a client.

What happened then? This stunt would be a grave offense for a professional translator. A certified/sworn translator would probably lose their certification for it. I'm guessing your translator was a cut-rate freelancer doing this work on the side with little connection to the professional translator community, which generally prides itself on its professionalism.

Also, no reputable translation agency that I know of gets their translators for UpWork. They either find them through word of mouth, translator associations, or sometimes translator communities like proz.com. They don't typically "post" jobs, rather they have a list of vetted translators who have signed their confidentiality and other contracts, and whom they then email individually to ask if they're interested in job X (usually attaching the job). And the more reputable ones have their own certification process or else only work with translators certified by a reputable body (ATA, ITI, etc.). Most reputable translation agencies will also have a second translator edit or proofread the document once it's been translated.