What changes hands is narrower than the download suggests. A marketplace sells permission to build a single end product, so a second client site assembled from the same files is a second purchase however much of the labour was copy and paste. The files themselves arrive in two shapes with very different futures. Flat templates are markup, styles and scripts you adapt and then live with: nothing updates itself, and nothing breaks when a platform ships a major version. A theme is that same design wired into a content management system, usually WordPress, so it inherits the hooks, the plugin ecosystem and the upgrade cadence of a codebase nobody on your side controls. That coupling is the real purchase, which makes the item page more informative than the demo, and why the entitlement to updates and support attached to a purchase is worth reading before the screenshots are.
Judge an item by its release history rather than by how well it photographs. Steady releases across several platform versions describe an author who is still present; a listing that went quiet is offering you a migration at a date of its choosing, and that migration reliably costs more than the original build. Ask what support covers and when it expires, since help with an item usually runs on its own clock and extending it later is normal rather than exceptional. Then weigh the thing. Best-selling items tend to bundle a page builder, a slider, a shop and a booking flow, and a brochure site running that bundle pays for every unused feature on every request, a cost your caching layer can hide but never remove. A narrower item from a present author wins more often than the sales rank implies. Where the same components keep reappearing across projects, extracting them into a design system closes the licensing question for good, since parts you own carry no grant to check and no renewal to miss.
Buy in the client's name
A grant belongs to whoever bought it, so an agency purchase does not travel with the site automatically at handover. Settle it at proposal stage: purchase under the client's account and rebill, or name the owner of every third-party licence inside the statement of work, renewal dates included. The alternative is a client who cannot get support for their own website and an agency still paying for software it no longer uses.