No, 24.90€ is not lifetime license for 10 iv nor 10 v devices. The one-time-fee (perpetual) Sailfish license for Xperia 10 IV and 10 V will be announced separately.
You get discount for the subscription fees (normally 4.99€/month) for the first 6 months for any orders made by end of April – valued 29.94€. That said, if you like you may still choose to support Sailfish OS development and community efforts with 24.90€ support package.