Custom e-commerce for the price of a Shopify subscription: TCO over 24 months

“A custom build is expensive because development is expensive.” That holds on a Friday evening. By Monday morning it's less obvious, because “cheap” SaaS platforms accumulate monthly cost faster than the founder who picked based on the landing page expects.

We ran exactly that calculator for MessyPlay. Here is the clean math — real numbers from a real project, without sweeping anything under the rug that custom genuinely costs.

Shopify cost (24 months)

MessyPlay was paying ~6 000 CZK/month for the full stack:

• Shopify Advanced: ~2 000 CZK/mo
• Course booking plug-in: ~600 CZK/mo
• CZ VAT + invoicing plug-in: ~800 CZK/mo
• Supplier integration plug-in: ~600 CZK/mo
• Loyalty plug-in: ~400 CZK/mo
• Theme customisation / ad-hoc dev: ~800 CZK/mo
• Transaction fee (0.5-1% of revenue): ~800 CZK/mo

24 months = 144 000 CZK in fixed running costs. Plus the founder's time lost fighting platform limits — which I can't price exactly, but it came up repeatedly.

Custom cost (24 months)

Replaced with an Azure-hosted app (.NET backend, React frontend, Azure SQL, blob storage, App Service):

• One-off development: ~200 000 CZK (6 weeks senior dev)
• Azure hosting: ~1 200 CZK/mo
• Reserve for small fixes / tweaks: ~1 500 CZK/mo
• Transaction fee: 0 (direct Comgate integration)

24 months = 200 000 + 28 800 + 36 000 = 264 800 CZK.

At first glance custom looks MORE expensive — by 120 000 CZK over 2 years.

Except — time is money too

Here's the line the calculator skips. On the Shopify setup, the MessyPlay founder spent an estimated 2-4 hours a week wrestling the platform — plug-in incompatibilities, update breakage, debugging why something doesn't render properly.

Conservatively: 3 h/week × 52 weeks × 2 years × 500 CZK/hour (founder's opportunity cost — time away from growing the business) = 156 000 CZK of hidden cost on Shopify.

On the custom build, the founder has a maintenance retainer with us. Typical monthly time spent is 30 minutes on “we want to change something” — 12 hours a year, 6 000 CZK.

Actual 24-month TCO

• Shopify: 144 000 (fixed) + 156 000 (time) = 300 000 CZK
• Custom: 264 800 (fixed) + 12 000 (time) = 276 800 CZK

Custom wins by ~25 000 CZK. A fraction of what build-vs-buy marketing usually promises, but a win nonetheless. Projecting 4 years: Shopify 600 000, custom ~400 000. The gap widens.

Where this math doesn't hold

It holds for shops with:

• Specific needs that force 3+ paid plug-ins
• Revenue high enough that transaction fees bite
• A serious growth intent (not a side project)
• An owner who doesn't want to spend hours each week on platform maintenance

It doesn't hold for:

• Validating a new idea / product-market-fit testing
• Shops under ~500 000 CZK annual revenue
• Shops that fit in Shopify out-of-the-box (zero plug-ins, zero customisation)

The takeaway

This calculator is specific to MessyPlay. But the shape repeats: platforms have MONTHLY cost growth tracking revenue; custom has ONE-OFF cost growth tracking features. Those two curves cross. The only question is when.

Do the 2-year TCO for your own shop on both sides. If custom is more than 30% pricier — stay on the platform. If comparable or cheaper — worth seriously considering. If 20% cheaper including the time cost — stop procrastinating.