OC,
I know this is know the answer you're looking for, but all I can share, is that WIN is at a combined 24,000 wpm (for 6'' GaAs) from 2 fabs and expected to reach 30,000 wpm by 3Q16.
Source : http://asiaresearch.daiwacm.com/eg/cgi-bin/files/Win_Semiconductors_150102.pdf
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Therefore, 50,000 (6" GaAs) wpm seems quite a high figure