Just think it as a break and get ready for another captcha solving frenzy 
If we can sell mrai for 500 sats each, how many do we need to make 1 bitcoin? Hmmm - 200,000 mrai = 1 bitcoin! Can we do that?
500 satoshi is not that high of a target, but there's little chance of someone earning whole bitcoin on it.
The last time i was gathering them , i often received only about 1 to 1.5 mrai per solved recaptcha.
It would take you insane amount of time to reach any reasonable figure with that mrai-bitcoin ratio, hence threads like this one are probably placed.