Sendinblue's paid plans start with the 10,000-email-a-month Lite plan, which costs $25 per month, billed monthly, and $22.50 per month billed annually. The amount of email you want to send impacts the price, though, so the Lite plan can cost between $25 and $99 per month, while the Premium plan can cost between $65 and $599 per month.
In addition, there's a free plan at no cost, and an Enterprise one for a custom quote.