Are free Amazon seller tools good enough?

Free tiers — Helium 10's limited plan, the FBA revenue calculator, basic Chrome extensions — are genuinely useful for learning and for low-volume sellers, and you should exhaust them before paying. Their limits are usage caps, shallow historical data, and no automation. Paid tools earn their keep once your sourcing volume, ad spend, or SKU count makes the time saved or the better decisions worth more than the subscription. Match the spend to the decisions it improves.