Heh... found this after some digging-- I actually found the memo I was looking for yesterday, but my eyes glanced over the stereo part...

Leslie Carey put together the breakdown. Since most of the stages were apparently equipped for mag recording (but not specifically stereophonic), that was not part of it. However, dubbing of THUNDER BAY in stereophonic sound was estimated at $5,000, and the expectation was that further films would cost about $3,000. Separate magnetic tracks for THUNDER BAY would cost about $425 per print. Since the film was longer than normal, the average magnetic tracks for a film (at Universal) would cost approximately $300 per print.

Ironically, the same day, they dropped the sepia-tone idea from IT CAME FROM OUTER SPACE because Columbia's MAN IN THE DARK, also sepia-tone, was playing at the UA downtown and had to upgrade from a 65 amp to 95 amp lamphouse to get a satisfactory image on the screen (cost: about $2,000). Apparently they were still deciding at that point, as there was a sepia print being shipped to be viewed that evening. Apparently they chose not to.