GHS StringsGB-DGF Boomers David Gilmour Electric Guitar Set - 10-48

what makes these strings so special?

Why is one pack of strings $5, but the 3 pack is $21? That doesn’t make any sense.

Managed to snap the high E string while tuning it for the first time with the new strings. Any way to replace just the one versus buying a new pack?

Won't these strings throw the guitar's intonation off if you normally use a regular set of 10s?