A solid mechanical keyboard with custom keycaps is an investment in your daily workspace. We want something built with an aluminum case and hot-swappable switches so you only buy once, rather than replacing cheap boards every year.
Watch the manufacturer drop releases for the board you want, but remember that last year's model often drops in price once the new version hits. That is usually when you get the best value without chasing hype.
Keep in mind that the intro window is a hard deadline, not free money. If you still carry a balance when those 18 months are up, deferred interest or standard rates will kick in on what is left.