Verified 2026 API Rates • Prompt Caching & Batch ROI

OpenAI: GPT-6.1 Terra vs Microsoft: Phi 4

Compare real-world API costs for OpenAI: GPT-6.1 Terra ($1/$5) vs Microsoft: Phi 4 ($0.07/$0.14). Calculate Prompt Caching ROI & Batch API savings.

Microsoft: Phi 4 saves up to 93% on base input tokens
OpenAI

OpenAI: GPT-6.1 Terra

gpt-6.1-terra
Base Input Rate
$1.00 / 1M
Output Rate
$5.00 / 1M
Prompt Cache Read
$0.050 / 1M (-95%)
Cache Write Surcharge
$0.00 (Free write)
Batch API Discount
-50% Off
Context Window
1,050k tokens
Quality Index (MMLU)
87.8
Microsoft

Microsoft: Phi 4

phi-4
Base Input Rate
$0.07 / 1M
Output Rate
$0.14 / 1M
Prompt Cache Read
$0.035 / 1M (-50%)
Cache Write Surcharge
$0.00 (Free write)
Batch API Discount
-50% Off
Context Window
16.384k tokens
Quality Index (MMLU)
78
Differential Module 1

Prompt Caching ROI & Write Surcharge Break-Even Analysis

Prompt caching drastically reduces input token costs for static prefixes like system prompts, tool schemas, and document chunks. Compare caching mechanisms between OpenAI: GPT-6.1 Terra and Microsoft: Phi 4:

OpenAI: GPT-6.1 Terra Caching Profile-95% read discount

  • Cached Read Price: $0.050 per 1M tokens.
  • Write Surcharge: $0.00 (automatic caching with zero write penalty).
  • Minimum Cache Prefix: 1,024 tokens.
  • Amortization Rule: Immediate net savings from first cached read call.

Microsoft: Phi 4 Caching Profile-50% read discount

  • Cached Read Price: $0.035 per 1M tokens.
  • Write Surcharge: $0.00 (automatic caching with zero write penalty).
  • Minimum Cache Prefix: 1,024 tokens.
  • Amortization Rule: Immediate net savings from first cached read call.
Differential Module 2

Batch API 50% Discount Offload vs Real-Time SLA

Asynchronous Batch APIs cut total token expenditures in half (50% off input and output) in exchange for non-realtime execution (up to 24-hour turnaround SLA).

Model / ArchitectureStandard Input / OutputBatch 50% Off Input / OutputTurnaround SLAOptimal Use Cases
OpenAI: GPT-6.1 Terra$1.00 / $5.00$0.50 / $2.50 (-50%)24 Hours max (typically 30m - 2h)Bulk evaluation, dataset labeling, background summarization
Microsoft: Phi 4$0.07 / $0.14$0.04 / $0.07 (-50%)24 Hours max (typically 30m - 2h)Offline document translation, embedding backfills, test suites
Differential Module 3

Context Window Escalation & Tiered Pricing Architecture

Massive context windows allow ingesting entire repositories or books, but pricing models differ drastically between flat-rate vendors and tiered step-up pricing.

OpenAI: GPT-6.1 Terra Context Capacity

Provides a 1,050k token context window with a maximum output limit of 128k tokens.✓ Flat-rate billing across all prompt sizes up to max context ceiling.

Microsoft: Phi 4 Context Capacity

Provides a 16.384k token context window with a maximum output limit of 14.745k tokens.✓ Flat-rate billing across all prompt sizes up to max context ceiling.

Quill Strategic Content

Real-World Production Scenarios: Monthly Spend Projections

Pre-computed monthly engineering bill projections across 3 representative enterprise application workloads:

Scenario 1

RAG Knowledge Base & Enterprise Search

100,000 queries/month, 3,500 input tokens (system + 5 retrieved chunks), 400 output tokens, 75% prompt cache hit rate.

OpenAI: GPT-6.1 Terra:$300.63/mo
Microsoft: Phi 4:$20.91/mo
Delta Savings:-$279.71 (93%)
Architecture Verdict:Microsoft: Phi 4 delivers 93% lower monthly spend ($279.71/mo savings) for this workload profile.
Scenario 2

Multi-Turn Coding Agent & ReAct Loops

25,000 tasks/month, 8,000 input tokens (accumulating conversation context & tool schemas), 1,200 output tokens, 85% cache hit rate.

OpenAI: GPT-6.1 Terra:$174.36/mo
Microsoft: Phi 4:$11.33/mo
Delta Savings:-$163.03 (94%)
Architecture Verdict:Microsoft: Phi 4 delivers 94% lower monthly spend ($163.03/mo savings) for this workload profile.
Scenario 3

High-Throughput Offline Data Extraction

500,000 records/month, 1,500 input tokens, 250 output tokens, 100% batch offload (24-hour turnaround SLA).

OpenAI: GPT-6.1 Terra:$616.25/mo
Microsoft: Phi 4:$32.38/mo
Delta Savings:-$583.88 (95%)
Architecture Verdict:Microsoft: Phi 4 delivers 95% lower monthly spend ($583.88/mo savings) for this workload profile.
毫秒級即時互動模擬引擎

OpenAI: GPT-6.1 Terra 對比 Microsoft: Phi 4

針對企業典型三大工程落地形態(RAG 知識庫、Coding Agent 多輪、離線批次清洗)進行精確成本演算:

Live 50ms Engine
月度請求量 (Requests)100,000
單次輸入代幣 (Input Tokens)4,000
單次輸出代幣 (Output Tokens)1,000
Prompt 快取命中率 (Cache Hit)70%
Batch API 批次分流比例0%
Microsoft: Phi 4 更便宜

預計每月節省

OpenAI: GPT-6.1 Terra$634.00$6.340// 千次請求
對比
Microsoft: Phi 4$32.20$0.322// 千次請求
Developer FAQs

Frequently Asked Questions: OpenAI: GPT-6.1 Terra vs Microsoft: Phi 4

Authoritative answers on API rate limits, pricing math, break-even thresholds, and architectural migration.

1Which model is cheaper overall: OpenAI: GPT-6.1 Terra or Microsoft: Phi 4?

At base pricing, OpenAI: GPT-6.1 Terra costs $1/1M input and $5/1M output, while Microsoft: Phi 4 costs $0.07/1M input and $0.14/1M output. The cheaper option depends on your input-to-output token ratio and whether prompt caching or batch discounts are utilized.

2How does Prompt Caching impact the cost of OpenAI: GPT-6.1 Terra vs Microsoft: Phi 4?

OpenAI: GPT-6.1 Terra offers a 95% read discount ($0.05/1M), whereas Microsoft: Phi 4 provides a 50% read discount ($0.035/1M). High cache hit ratios (>70%) significantly compress the cost delta in agentic and RAG architectures.

3Can I use Batch API with OpenAI: GPT-6.1 Terra or Microsoft: Phi 4 to save 50%?

OpenAI: GPT-6.1 Terra supports 50% batch offload discounts for asynchronous 24-hour turnaround tasks. Microsoft: Phi 4 supports 50% batch discounts.

4What are the context window limits and tiered pricing rules for OpenAI: GPT-6.1 Terra vs Microsoft: Phi 4?

OpenAI: GPT-6.1 Terra features a 1,050k context window with flat per-token pricing. In comparison, Microsoft: Phi 4 supports 16.384k tokens with flat per-token pricing.