Engagement Hub — AWS Cost Model

Conservative estimates · ap-southeast-2 (Sydney) · Jun 2026 · Real production billing + 139 AI token samples (P90)
AUD
AWS Cost / practice / month
Infra (fixed)
Infra (variable)
AI (Bedrock)
Total cost
Revenue / practice / month
Practice fee
Advisors
Admins
Clients
Total revenue
Profit & Margin / practice / month
Gross Profit
Margin

Pricing Package
Fees (AUD)
A$50
A$25
A$10
Client Fee Bands
BandClientsA$/client/mo

Team per practice
2
2
100

Practice fee is monthly recurring
AI cost included in price
AI Job Volumes (jobs / month)
Unit Economics — 1 Practice
Practice count: 1

Scale Projection

Revenue and cost trajectory as practices grow. Fixed overhead amortises rapidly — margin improves at scale. All figures in AUD.

Revenue vs AWS cost by practice count (AUD)
Gross margin % by practice count
Practices Revenue/mo Infra cost AI cost Total cost Profit Margin

Infrastructure Cost Structure

May 2026 actuals · ~1.5 active practices · ap-southeast-2 · USD costs converted to AUD at current rate

Cost breakdown by service (May 2026)
Service May (USD) May (AUD) Type Per practice (AUD)
Variable cost per practice: (conservative; USD $3.00 × rate).
Fixed overhead: /mo shared — amortises rapidly at scale.

AI Feature Costs

Adjust monthly job volumes to model usage scenarios. Token data from production logs (P90 conservative — 139 samples).

Total AI cost / practice / month (AUD)

Actual AWS Billing — Validation (USD)

Bedrock vs Infrastructure spend (Mar–May 2026, USD)
Month Bedrock (USD) Infra (USD) Total (USD) Note
Mar 2026 $13.61 $5.59 $75.16 Incl. $48 domain + dev costs
Apr 2026 $36.31 $7.35 $48.04
May 2026 $29.20 $10.16 $43.30
March anomaly: $75.16 total includes a $48 one-time annual domain charge and ~$13.50 in US East dev/test costs. Normalised AU infra is $5.59. Infra trend Mar→May: $5.59 → $7.35 → $10.16 reflects S3 accumulation.

Free Tier Scale Thresholds

Lambda, Cognito, CloudWatch, SNS, KMS all billed $0.00 in May 2026. Current usage at ~1.5 practices.

Service May usage Free limit Breaks free tier at
Lambda 23,907 GB-Sec (6%) 400,000 GB-Sec/mo ~25 practices
Cognito 898 MAU 50,000 MAU ~83 practices
CloudWatch Logs 0.57 GB-Mo 5 GB/month ~13 practices
SNS 74 notifications 1,000/month ~20 practices

Cost Optimisation Opportunities

Prompt caching — Compliance Coach ~40% AI saving

165K input tokens per call with zero caching. System prompt is ~70K constant tokens across all calls.

Scenario Cost / call (AUD)
Current (no cache)
With prompt caching
Saving per call
Prompt caching — AI Reports ~40% AI saving

134K input tokens per call with a large fixed template. Caching could save 40–50% on repeat calls within the TTL window.

Scenario Cost / call (AUD)
Current (no cache)
With prompt caching
Saving per call
Model tiering — extraction tasks ~80% saving on sub-task

Action item extraction runs on Sonnet at $3.30/M input. Claude Haiku 3.5 costs $0.80/M input — same quality for short extraction tasks.

Model Cost / extraction (AUD)
Sonnet 4.5 (current)
Haiku 3.5
Saving per call
S3 lifecycle policy Ongoing cost risk

45 GB stored in S3 as of May 2026 (~30 GB/practice) with no expiry rule. AI outputs accumulate indefinitely — S3 nearly doubled Mar→May. Recommend: S3-IA after 90 days, Glacier after 365 days. Estimated saving: 40–60% of storage costs at steady state.


Data Confidence

Cost item Source Confidence Note
Infrastructure costs May 2026 AWS invoice High Real billing, ap-southeast-2
Bedrock pricing AWS console, Jun 2026 High Confirmed Sonnet 4.5 & 4.6 rates
AI token usage 139 production log samples High P90 across 5 features
INFRA_VARIABLE (USD $3.00/mo) May actuals ÷ 1.5 practices Medium 7% buffer above actual $2.79
S3 storage model 45 GB observed, May 2026 Medium Cumulative — no lifecycle policy yet
Scale projections Linear extrapolation Medium Lambda free tier expires ~25 practices