Custom Subscriptions & Recurring Billing vs SaaS: Costs in London in 2026

The verdict in three sentences

A subscription model means recurring billing, dunning and customer lifecycles — not just a "subscribe" button. With SaaS (Recharge, Stripe Billing) you pay a percentage of recurring volume for life; with custom, you amortize a one-off build of 18,000-40,000 EUR. The 2026 tipping point lands around ~1M EUR of annualized MRR: beyond that, the SaaS % exceeds the amortized custom build.

What each model costs

Custom finely handles cycles, upgrades/downgrades, pauses, proration and dunning — rules that are often capped or costly in SaaS.

The tipping point, quantified

Compare the annual SaaS % cost to amortizing a 30,000 EUR build (over 3 years = 10,000 EUR/yr + 5,000 maintenance = 15,000 EUR/yr).

Below ~1M EUR of recurring volume, SaaS is unbeatable for simplicity and cost. Beyond that, custom becomes profitable — and frees you from third-party dependency.

Dunning and involuntary churn: the hidden line item

Involuntary churn (expired cards, declined payments) can be 20-40% of total churn. A good dunning system (retries, smart re-attempts) cuts it sharply.

Mini case study

Ms. Clarke, director of an eco-friendly cleaning products e-commerce in London, launches a monthly subscription offer. Year 1, her annualized MRR targets 400,000 EUR: she starts on Stripe Billing (~0.6% ≈ 2,400 EUR/yr extra cost), with no heavy build. Year 3, recurring volume reaches 1.8M EUR: the SaaS % would cost ~10,800 EUR/yr and cap her pause/proration logic. She migrates to a custom engine at 30,000 EUR, amortized over 3 years (10,000 EUR/yr + 5,000 maintenance). With involuntary-churn recovery (+35% on failed payments), the net gain exceeds the cost by the second year post-migration.

FAQ

When to stay on SaaS? As long as your annualized MRR is below ~1M EUR and your subscription rules are standard. Stripe Billing at 0.5-0.7% stays cheaper than amortizing a build.

When to go custom? Beyond ~1-1.5M EUR of recurring volume, or as soon as your rules (pauses, proration, bundles, complex upgrades) are costly to work around in SaaS. The build runs about 18,000-40,000 EUR.

How much is dunning? Built into the custom engine for 3,000-6,000 EUR, it can recover 30-50% of involuntary churn — often the highest-ROI item.

Can we start SaaS then migrate? Yes, that's the safest path. Plan the migration of active subscriptions and payment methods (3,000-8,000 EUR depending on volume).

Does custom include payment compliance? It relies on a PSP (Stripe, etc.) for PCI compliance; you handle subscription logic, not card storage. That sharply reduces regulatory risk and cost.

Let's scope your project. Tell us your target MRR, your subscription rules and your PSP, and we'll price SaaS vs a custom engine and the tipping point. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.