iPhones come in fixed storage configurations, with the most affordable versions offering lower storage. Even though the current generation iPhone 15 Pro starts at 128GB, many older generation iPhones start at 64GB. iOS itself takes up upwards of 10GB of storage. The only way you can ensure you don’t run out of storage on your great iPhone is either to opt for a higher storage capacity variant or buy an iCloud subscription with extra cloud storage space, which can set you back by $2.99 per month for a 200GB plan.