Inelasticity of demand from complementary goods comes into play when the complementary good is relatively very expensive or difficult to replace.

Consumer printers cost about the same as an ink cartridge or two. Consumers aren't "stuck" paying for more expensive ink if manufacturers decide to start screwing them on the price.

[edit: wanted to add this] Even with the ridiculously complementary goods of automobiles and gasoline, more expensive gas shifts consumer demand away from gas guzzlers.