Chances are if they are honest and have the budget to spend 4K/month, they’d order a paid test translation. In which case, you don’t lose anything (of course, that is, only after carefully checking the file, like Hans suggests, else, you might lose time to de-virus your pc and change all your passwords and so on ;))
You could offer them to do the test page for $5 or $10 or whatever you’d take for a page usually and see how they’ll react.
Of course, if they expect you to do the test for free, and it’s “just” a page, it’s up to you if you want to invest that time with perhaps no result, but with a budget like that, I honestly can’t see why they’d not offer to pay for the test translation, so, yeah …
And as ahmwritingco said, you never know. Even beyond an offer being placed, as many forum posts show.
In case the test translation and all happens and goes well and it gets to an order, you might want to consider discussing terms that are better for you, like not working a whole month for 4K but to split the month’s work up.
Remember that if your delivery time for the order is 30 days, you’ll work for 30 days (+ 3 days until autocompletion if they don’t complete the order) + 14 days clearance period before you’ll have the money. And there is always the possibility that they might try to cancel the gig then, once they received your delivery, so it would be much better to find that out after a week than a month.
5000 words per day, by the way, is a pretty crazy workload for manual/good quality translation. Personally, I couldn’t accept that as I can only work so and so many hours a day, and I have the feeling that people who know what they are doing, should know that that’s an insane daily amount to expect too. Actually, as that would be a (more than!) full-time job for just 1 single client, it would not be regarded as a freelancing job but as concealed employment at least where I am and might lead to trouble.
I also think with a workload that high, they’d not be looking for 1 single person but for several freelancers to distribute it to, so they’d not have to wait a whole 30 days to get their files, and also would not fall back a whole week or maybe two if their 1 freelancer is sick or on vacation, …
Are you prepared to only work for a single person 7/7 every month (who might turn out to not be legit), maybe even lose regular customers because you can’t find time for their orders? A lot of things to consider there, if they turn out to be frauds, after all, only after you worked a whole month for them, you’d have lost a lot of money/time.
Well, as you already guessed, it does not sound quite normal to me. But, yeah, you never know.
I’ll be following the thread to see if they’ll pay for the test translation and if you end up accepting to work for them, and on what terms, and how it will turn out.