Talk about exploitative. Hell, that's incredibly biased. Can you imagine a young parent being able to do that?
At least they are open about it. It is probably a fair indication of the companies values if they are oblivious to how unreasonable a 3 day take home assignment is.
Most cheapo shops which won't pay FAANG salaries but still want near-FAANG-quality-engineers end up using this as a bait.
Other ways are "your work has great purpose!" "You will advance humanity!" "You will bring great experiences to users" ... yeah yeah yeah, just an alias for "we are a glorified bodyshop. BigCos hire us for some piecemeal job. We get it done and get paid relatively well." But this isn't too appealing, is it!
It would most probably have a twisted answer as "you can post that solution of yours in your git repo and showcase it as a part of your portfolio"
Many shops out here are so adept at this stuff, it's no more funny!