EC Site Development Costs — Where ASP/SaaS Carts and Custom Builds Diverge

An EC (e-commerce) site is a website where customers can order and pay for products or services online. Build costs range from nearly free with an ASP/SaaS cart to tens of millions of yen for a fully custom (scratch-built) system, and the choice of approach affects both upfront and ongoing costs significantly. This article neutrally outlines cost tiers by build method and the factors that drive costs up or down. Figures here are general estimates only — actual costs depend on requirements, so getting quotes from multiple vendors is recommended before deciding.

- Build method: whether you choose an ASP/SaaS cart, an open-source platform, or a full custom build can change upfront cost by an order of magnitude
- Number of SKUs: once you exceed a few hundred products, inventory and search functionality need more custom development
- Payment methods: adding options beyond credit cards — cash on delivery, deferred payment, carrier billing — increases setup and screening costs
- Integration with existing systems: whether the site needs to sync data with inventory or accounting systems
- Design originality: reusing a template versus a fully original design
- Multi-language / multi-currency support: needed for cross-border e-commerce, and adds implementation cost
- Ongoing maintenance: whether operations are handled in-house or outsourced, and how often updates are needed

The table below shows general cost ranges by build method. These are rough market benchmarks that can shift up or down depending on functional requirements and product volume — comparing quotes from multiple vendors is the best way to confirm an accurate figure.

Comparing only upfront costs can be misleading. Most ASP/SaaS carts charge a fixed monthly fee plus a transaction fee of roughly 3–7% of sales. As monthly sales grow, this fee accumulates, so a lower upfront cost doesn't necessarily mean a lower total cost. A fully custom build has a higher upfront cost, but contracting directly with a payment processor can sometimes secure a lower transaction fee rate. In addition, many SaaS carts are tiered by product count or traffic volume, so as a business grows it may need to upgrade to a higher plan — pushing monthly costs above initial expectations. Checking each plan's limits (product listings, image storage, concurrent traffic) and the cost of exceeding them before signing up helps avoid unexpected cost increases later.

- Real-time integration with inventory or accounting systems is a business requirement
- The business needs tiered membership pricing or complex ordering logic
- Growth projections suggest that cumulative transaction fees will eventually exceed the cost of a custom build
- The business has industry-specific commercial practices (quote-based pricing, invoiced payment terms, etc.) that existing ASP/SaaS carts can't accommodate

It's best to compare build methods on a multi-year total cost basis — including monthly fees, transaction fees, maintenance, and future feature additions — rather than upfront cost alone. ASP/SaaS carts tend to have lower upfront costs but fees and monthly charges accumulate over time, while custom builds have higher upfront costs but tend to keep variable monthly costs lower. Which approach comes out ahead depends heavily on how sales volume and product count grow, so there's no single universal answer.

One cost that often gets overlooked is the labor involved in day-to-day operations — listing products, updating inventory, processing orders, and handling customer inquiries. This ongoing work is required regardless of which build method is chosen, and whether it's handled in-house or outsourced changes the monthly running cost independently of the system fees themselves. When comparing quotes, it's worth factoring in this operational overhead alongside the platform costs.

- Sort required functionality into "must-have" and "nice-to-have" before choosing a build method
- Estimate annual transaction-fee cost as "projected monthly sales × fee rate" and compare that across methods
- Migrating from an ASP to a custom build involves data migration and SEO continuity costs, so factor in future business scale from the planning stage
- Get quotes from multiple vendors for the same requirements, and compare upfront cost, monthly cost, maintenance cost, and future development cost side by side
- For general guidance on the ordering process, see the system ordering guide; for cost-reduction approaches, see how to reduce development costs

EC site build costs vary enormously — from tens of thousands of yen to tens of millions — depending on the build method, product count, payment methods, and integration requirements. It's important to compare total cost, including monthly fees and transaction charges, not just upfront cost, and to choose an approach that matches your business scale and growth plans. When in doubt, it helps to request quotes from multiple vendors against the same requirements and compare the breakdowns before deciding.