In the original draft of Fifth Edition, dwarfs were going to have +10% gear and lifestyle costs, and trolls +50% gear and lifestyle costs. Then someone realized the chronic bookkeeping headache that would impose on dwarf and troll players, and they decided to bundle it all into Lifestyle costs instead (+20% for dwarfs, +100% for trolls) and leave the gear costs alone. They missed a few references in the first printing (p.67, 94, 95), but I think they've cleaned it up since.
So yeah, if you walked into a Weapons World outlet at the local mall in 2075, a troll-size armor jacket would probably cost more than a human-size one, but the price tag in the rulebook is the same, and the difference is bundled into the troll's Lifestyle instead. Easier that way.