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AnonymousRand, you are comparing a bid of $1,000 (without vig) to $1,320 (with vig). You need to compare $1,000 to $1,210 (both numbers before the vig) or $1,200 to $1,452 (both numbers after the vig) which is 21% in either case.
But no, in the long run it does not benefit the consignor. It comes out even. They will sometimes gain when a bidder reluctantly jumps up the large increment but will sometimes lose when a bidder won't jump up because the increment is too large.