Yes, I agree with you that 4K need huge amount of storage space especially when you want to keep the recording for longer period of time.
This IP camera has H.265 and also Smart H.265 support, which can further reduce the storage and bandwidth requirement for recording and streaming.

If one have the budget to put 4K camera for the whole house, the person should have no problem to install more storage for recording.
For me, I just purchase 2 units of them to play with it. 

From my observation, hard disk for surveillance usage is getting cheaper now.
For example WD 4TB Purple hard disk, I bought at around RM 680 two years ago, now cost only RM 430 per piece.