Yes storage is relatively cheap these days, but only for those phones where you can add cards. iPhones do not have card slots to add storage so you're stuck getting their overpriced internal storage if you want to use the Apple ecosystem.Are you out of your mind?
A 128gb micro SD card is around $15 bucks. If you can't afford that you Probbly shouldn't be driving a truck that uses gas and ride a bicycle everywhere.
The size of audio files are the same no matter what you put it on. Storage is more expensive using CDs then anything else. Are you remembering the music and humming it to your self instead of playing it on a device because it's too expensive to store on a digital recording device?
I respectfully disagree - the size of audio files are not the same (unless you mean copying one file to multiple devices then yes). Not only can you rip mp3s at different bit rates that result in varying file sizes, but there's other file formats that can be used (on UC5 at least) like flac (which is a lossless file). I've got a mixture of flac and mp3 files on a 1 Tb SSD hooked to the USB-C port. I can store my whole collection on it. It's way more than I have on my phone.