I didn't use masters for mine because it was easy enough for me to look at the email addresses that were coming in and see if they were junk.

Would be curious to find out if masters will work for $.05. Please keep me posted! :)

In 2 hours I had 2 HITs completed by masters. Probably going to need to switch to regular workers and closely monitor like you did.

One approach is to get each hit done by two (or three) regular MTurkers and crosscheck the results. I've seen this done with "human OCR" type tasks.

The masters qualification is handed out to the top tier workers. It's for people who basically use mturk for a full time job and 'usually' output extremely high quality work.

The masters qualification is supposed to open up the higher paying tasks. They will calculate the cost and if they aren't earning, at minimum, .10c per min or better, they will abandon or return your hits. Keep in mind that probably less than 1% of all turkers have that qualification. It's extremely tough to get.

I mean no offense, but requiring a masters qualification for your (being blunt) junk hits is like requiring a PhD to flip burgers at McDonald's.