I suppose the payout in terms of profit is even less on average (80% DIV 90 days) - but still suspiciously high.
It's probably because I don't know the details of the tumbling algo - if the majority of the output from the tumbler comes from other 'tumblers', to which they don't pay interest and investors are only adding to the liquidity then it would make sense.
I really like their website, they put a lot of work into it, indicating that they aren't going away any time soon. Did some DD around their company registration and webhosting, it all checked out. Now just trying to justify a larger investment to myself than the 1 ETH I currently put in just to try it out :)
RE: Thunderbit is Paying Out - Bitlake Bit the Dust - Bitpetite New Tumbler Service