What’s “dev ongoing” — what does it cover?

The yearly dev/maintenance retainer needed to keep the store operating after launch. Covers:

• Bug fixes + uptime. Production issues during business hours (and after-hours if you have an SLA in the retainer). Typically 5–20% of monthly hours.
• Feature iteration. A/B tests, copy + UX changes, new payment method onboarding, new region launch, seasonal landing pages. 30–50% of hours.
• Security patches + version upgrades. Magento ships 2–3 minor versions a year. Adobe Commerce releases monthly security patches. Shopify Plus and SFCC handle this themselves (you save here). Plan for 5–15% of hours.
• Extension / app updates. Each extension you ship needs maintenance when its dependencies (Magento core, payment gateway API, third-party SaaS API) change. 5–10% of hours.
• Performance tuning. Cache warming, indexer optimisation, query analysis. 5–10% of hours.
• Monitoring + alerting. New Relic / Sentry / Datadog setup + on-call rotation if you have one. 5% of hours.

Rough sizing in the calculator:

• Magento Open Source under $5M GMV: $15k/yr (~150 hrs/yr at $100/hr)
• Magento Open Source $5M–$25M: $30k/yr (~300 hrs/yr)
• Magento Open Source $25M+: $60k/yr (~600 hrs/yr)
• Adobe Commerce: ~80% of Magento OS — less ext maintenance because B2B/RMA are native
• Shopify Plus: ~50% of Magento OS — no version upgrades, smaller surface area
• BigCommerce: ~60% of Magento OS
• SFCC: 100–200% of Magento OS — SI partner premium dominates

If you’re running on a $1.5k/mo retainer (~$18k/yr) and your store does $10M+ in GMV, you’re probably accruing tech debt. The calculator’s “dev ongoing” line is what it actually costs to keep things healthy.