The Double Showcase Rule
On daytime shows, beginning on or around April 15, 1974, if the winner bid less than $100 below the actual price of their own showcase, the contestant won both Showcases. To reflect inflation, the margin was raised to $250 or less beginning with Season 27 in 1998. The rule has been adopted on all CBS prime time versions since 1986.
If there is a tie where the differences are within the Double Showcase range, both contestants would win both Showcases. This has never happened, although on March 24, 1975 the contestants' differences were $30 and $29.
Beginning on the Season 36 prime time specials, to accommodate the higher value of Showcases presented in prime time (usually over $80,000), a $500 (originally $1,000 in the first six taped specials) range has been implemented. A $1,000,000 bonus is also awarded with a Double Showcase Win on these special episodes only.
Bidding $1
As some contestants often do in the One Bid round, contestants have also bid $1 (or another amount generally less than $10,000) on their Showcase hoping that the other contestant has overbid. This is rare and is generally only used if the other contestant's overbid is very obvious.
The first instance of an intentionally-low bid was on the September 7, 1972 episode (the third one taped), in which a contestant bid $500 on her Showcase (her opponent did indeed overbid). Due to this low bid, her Showcase price remained unrevealed, although people have confirmed that the price was $2,364 for a difference of $1,864.
It is unknown if such a strategy has ever backfired on a contestant who bid an intentionally low amount, only to find out that their opponent did not overbid.
Ties
If the two contestants are exactly the same distance from the actual prices without going over (a tie), each wins their own Showcase. This has happened at least once in the show's history, on an episode of the first nighttime season with Dennis James.
Perfect Bids
On the original version which aired on NBC and ABC, perfect bids by home viewers on the Showcases were rather common ? including an instance where a tie had to be broken among fourteen perfect bids.
Until December 2008, it was believed that there was only one perfect bid in the Showcase since 1972. The perfect bid occurred on the 1970's nighttime version hosted by Dennis James, but because there was no Double Showcase Rule on this nighttime syndicated version (or at least at the time), the contestant only won their own Showcase. The podium purportedly displayed "00000".
However, on the episode aired December 16, 2008 (taped September 22), a perfect bid occurred for the very first time on the daytime show. Unlike the first time this happened, this second perfect bid resulted in the podium displaying "0". Previously, the closest anyone had bid to their Showcase without going over was $1 (March 5, 1980), which aired exactly one week after a $2 win (February 27).
While it is legal to hear bid ideas from audience members, on that September 22, 2008 taping, CBS Standards and Practices and host Drew Carey were both suspicious of some audience members during the bidding. As a result, there was a 45-minute stopdown between the Showcase presentation and reveal on that taping. Some in the audience noted Carey's reveal was related to the suspicion that the production staff had on the win.[1]
Finally, there have been at least two people who overbid by $1 (and thus lost) ? on July 12, 1974 and October 19, 2004.