> Third, in your fabricated scenario, a fourth company would just come in and buy the (fictitious) discounted parts and win the bid. That's how the free market works.

So if there isn't a fourth company, yes there will be a premium paid due to the boycott. Your claim is essentially that if the winning bidders don't engage in the boycott then the boycott will not have an effect. Sure, but if the winning bidder does engage in the boycott, it will have an effect on cost.