I mean, between the 2 pila used by the first two front lines of their heavy infantry compared to the 7 javelins of their light infantry, maybe ? The author does insist on the expense.
Also, this was to compare with RimWorld, where pila are made with wood, and wood only. (While IRL your typical spear would have less metal and more wood than a pilum ?)
Factorio was in open alpha/beta for 8 years… xD