IMDb has a small little blurb about the effect of the Oscars on the box office. According to them hasn't been a big push for any of the Oscar winner. Only Brokeback Mountain and Crash saw any advances, and they were minimal compared to the success of Harry Potter and the Goblet of Fire.
Respectfully, I say to the writers at IMDb: "Duh!"
Of course the successes of "Crash" and "Brokeback Mountain" pale in comparison to Harry Potter. So did their initial costs. With the budgets of these films, even a small bump can cause great profits. Honestly what did IMDb expect? --Terrence Ryan