Broadway sales slipped slightly in Week 30 (Dec. 19-25), as most shows played a seven-performance week, gearing up to play an extra show during the sesh between Christmas and New Year’s, traditionally the most profitable frame of the year.Of the 34 productions on the boards, 20 played seven perfs rather than the usual eight during the frame that included Christmas Day, bringing the Rialto cume down by about $1 million to $23.3 million. Some shows managed to uptick despite fewer performances — most notably “Godspell” ($341,203), which climbed by about $50,000. The frame also underscored which shows reap the heftiest proportional benefits when tourists are in town. “The Phantom of the Opera” ($1,038,045) jumped up by a whopping 36% and “Mamma Mia!” ($704,380) stepped up by 26%, with both musicals playing the usual eight shows. Meanwhile, “Wicked” ($2,107,015) topped the week, ahead of “The Lion King” ($1,981,442). The 25 musicals grossed $20,125,218 for 86.5% of the Broadway total, with attendance of 190,178 and an average paid admission of $105.82. The nine plays grossed $3,145,863 for 13.5% of the Broadway total, with attendance of 41,938 and an average paid admission of $75.01.