Torrenting doesn’t deal well with updating files.
And you have another problem: how do you handle bad actors spamming the download ?
That’s probably why github does that.

You can calculate it !
Take your power usage and compute the cost over a year.
I will soon add a SSD because i finally moved from a RAID 1 to RAID 5 (so more HDDs), it consume more electricity.
I can measure how much power it draw because the server is on a smart plug. I calculated an additional 20-30€ a year of electricity, adding a SSD for read/write cache would allow the HDDs to stop spinning, make things faster and will be cost effective over a few years.

Consider that a new power efficient CPU may be cheaper by consuming less electricity over a few years!