Broadway box office continued to pick up in Week 17, (Sept.19-25), with “Follies” becoming one of the rare Stephen Sondheim tuners to crack the single-week $1 million mark and one-act play anthology “Relatively Speaking” bowing strongly in its first frame of previews.Rising in the wake of enthusiastic reviews, “Follies” ($1,122,778) climbed more than $245,000 to join the millionaires club, a feat few of Sondheim’s cerebral musicals manage to accomplish. The only other such success was “A Little Night Music” a couple of seasons ago, fueled by topliners Catherine Zeta-Jones and Angela Lansbury. “Follies” joined five other shows that took in more than $1 million for the week, including “The Book of Mormon” ($1,293,272), which again beat out “Spider-Man: Turn Off the Dark” ($1,269,403) in a venue that’s significantly smaller than the “Spider-Man’s” Foxwoods. “Relatively” ($716,252) — the triple-bill of comedies by Woody Allen, Elaine May and Ethan Coen — averaged houses filled to 98% capacity over its first eight previews. That’s a solid showing for a play whose scribes are seemingly well-known enough to provide a jolt of marquee appeal. Another addition, “The Mountaintop” ($411,044 for five previews), also added coin to the Rialto pot. The two-hander, which stars Samuel L. Jackson and Angela Bassett, reported auds that averaged about 87% of capacity. The Broadway cume climbed an impressive $2.5 million to $18.5 million for the 22 shows running, while overall attendance climbed by more than 25,000 to 206,595, hitting 88% of capacity. That attendance is about on par with last season at this time, although with 28 shows running in 2010-11, it came to only 81% of the sesh’s capacity. The 18 musicals grossed $16,127,344 for 87.3% of the Broadway total, with attendance of 181,061 at 87.3% capacity and average paid admission of $89.07. The four plays grossed $2,342,423 for 12.7% of the Broadway total, with attendance of 25,534 at 98.3% capacity and average paid admission of $91.74.