GPT-5.5 vs Gemini 2.5 Pro Multimodal Benchmark: Decoding the 71x Pricing Gap

Two flagship multimodal models landed within 30 days of each other, and the procurement question writes itself: do you pay $71 per million output tokens for GPT-5.5, or $1.00 for Gemini 2.5 Pro? That is a 71x difference on the exact same task. I spent the last two weeks running both models through image reasoning, PDF extraction, and chart-QA workloads on HolySheep AI and on direct vendor endpoints, and this guide is everything I wish someone had handed me before I started.

Provider Comparison at a Glance (Multimodal Output, per MTok)