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  5. ChatGPT-4o (March 2025)vsMercury 2.5
Updated Sep 2026

ChatGPT-4o (March 2025)vsMercury 2.5

Mercury 2.5 is cheaper than ChatGPT-4o (March 2025) at $0.04/M vs $5/M input tokens.

ChatGPT-4o (March 2025) and Mercury 2.5 compared across 3 shared prompts
SpecChatGPT-4o (March 2025)Mercury 2.5
Input price$5/M tokens$0.04/M tokens
Output price$15/M tokens$0.15/M tokens
Context window128K tokens260K tokens
Free API (OpenRouter)NoNo
ReleasedMar 2025Sep 2026
Side by side

Same prompt, both answers

Opening lines from 2 of the 3 prompts both answered. Formatting stripped, words untouched.

Simple 7-Ingredient Recipe

Create a simple recipe for a delicious dish (sweet or savory) using only 7 common pantry ingredients. Include a creative name for the dish…

ChatGPT-4o (March 2025)265 words
Recipe Name: Maple Cinnamon Toast Bites Description: A quick and delicious sweet treat made with pantry staples! These Maple Cinnamon Toast Bites are crispy, warm, and coated with a comforting blend of cinnamon and maple syrup. Perfect for a cozy snack or a fun breakfast twist.
Read the full answer
Mercury 2.5190 words
Pantry Pasta Primavera Prep Time: 5 minutes Cook Time: 15 minutes Servings: 2 Ingredients (7 Common Pantry Items) Pasta (spaghetti, penne, or fusilli) – 8 oz Canned crushed tomatoes – 1 can (14 oz) Olive oil – 3 tablespoons Garlic powder – 1 teaspoon Dried oregano – 1 teaspoon Parmesan cheese (grated) – ½ cup Salt and…
Read the full answer

Explain Like I'm a Specific Expert

Explain how a large language model (like GPT or Claude) learns and generates text to each of these three audiences: 1. **An experienced…

ChatGPT-4o (March 2025)704 words
Certainly! Here's how to explain large language models (LLMs) like GPT or Claude to each of your three audiences, with framing and emphasis tailored to their backgrounds and concerns: The Experienced Software Engineer Think of a large language model as a massively distributed, probabilistic autocomplete engine trained…
Read the full answer
Mercury 2.5572 words
For the Experienced Software Engineer Think of the model as a stateless microservice that has ingested the entire public internet as its training dataset. During the training phase, it performs a massive distributed optimization job, adjusting internal weights to minimize a loss function based on next-token prediction.
Read the full answer
Our Verdict
ChatGPT-4o (March 2025)
ChatGPT-4o (March 2025)
Mercury 2.5
Mercury 2.5

Not enough votes to call it. On the specs, nothing separates them.

Mercury 2.5 costs 100x less per token.

Too close to call
API pricing

Cost per 1M tokens

ChatGPT-4o (March 2025)
Input
$5.00
Output
$15.00
Mercury 2.5
Input
$0.04
125× cheaper
Output
$0.15
100× cheaper

Mercury 2.5 is cheaper on both: 125× input, 100× output.

Where to run it

1 host

ChatGPT-4o (March 2025)

No hosts listed on OpenRouter.

Mercury 2.51 host
HostInOutContextUptime
Inception$0.04 in·$0.15 out·260k·100% up

Per million tokens. Prices and uptime via OpenRouter, checked 22 Sep 2026.

Research

What we learned reading every model

FAQ

Common questions

ChatGPT-4o (March 2025) is developed by OpenAI while Mercury 2.5 is developed by Inception. ChatGPT-4o (March 2025) has a 128K token context window vs Mercury 2.5's 260K. You can compare their actual outputs across 3 challenges on Rival to see how they differ in practice.

It depends on your use case. ChatGPT-4o (March 2025) and Mercury 2.5 each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 3 challenges so you can judge which fits your needs best.

ChatGPT-4o (March 2025) costs $5/M input tokens and Mercury 2.5 costs $0.04/M input tokens. Mercury 2.5 is $4.96/M cheaper per input. Check their side-by-side outputs on Rival to see if the price difference is justified by quality.

This page shows a side-by-side comparison of ChatGPT-4o (March 2025) and Mercury 2.5 across shared challenges. You can vote on which model produced the better output in a blind duel. Browsing and voting are free. No account is needed to look; signing in only saves your votes and likes.

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Model pages

ChatGPT-4o (March 2025) logo
ChatGPT-4o (March 2025)33 outputs, specs and price
Mercury 2.5 logo
Mercury 2.53 outputs, specs and price
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