Unlike prices under the legacy perpetual licensing model, which were different between a new license (Year 1) and support updates in subsequent years, the subscription plans have the same fixed annual price.
Under the subscription-based licensing model, it will cost you much less to purchase NEW licenses (Year 1). Over a period of 3 years, depending on your exact plan, it should cost you under a subscription plan about the same as under perpetual terms. However, you will have access to all the future technology evolutions of IDA Pro if they choose a subscription plan, starting with IDA Pro 9.0.