Identify the actual constraint
A custom storefront makes sense when the browsing, catalogue or content needs are clear enough to justify tailored design and implementation. A smaller retailer with standard products may be well served by an established commerce service. Custom code should solve a specific requirement.
A storefront is only part of a store
A store also needs payments, stock records, order handling, delivery information, returns and customer communication. These are operational requirements. Decide which system is responsible for each before choosing how the storefront will be built.
Keep payments with an appropriate provider
A hosted checkout can keep card entry within a payment provider’s service. Integration still needs testing for successful, cancelled and failed payments. Provider fees and account approval sit outside the website build and should be checked before committing to the implementation.
Plan for maintenance
Products change, integrations evolve and browsers are updated. A custom store needs a maintenance plan and a person who can work with its source. Receiving the code is useful, but documentation and a list of dependencies make it easier to maintain.
Compare lifetime effort
Compare the initial build, recurring subscriptions, update effort and the cost of moving later. A custom store is worth discussing when these trade-offs fit the business. It does not guarantee additional sales.