Sophia here from Shopify. Welcome to the Shopify Community!
Whether you buy a domain from Shopify or a third-party registrar, the cost may change over time, though it's not guaranteed to go up after the first year.
Changes in renewal pricing depends on factors like the TLD. The costs for generic domains (like
.ca) don't change often. Special domains like
.store are typically priced higher and may offer an introductory price for the first year, resuming regular price for subsequent years.
Be sure to review the ICANN policy and Domain Registration Agreement when purchasing your domain, as these might provide more insight into the costs for your specific domain. Do you have a domain in mind for your store? Let me know what TLD you're thinking of using and I'll check to see if I can find any more information on the pricing for it.