While I agree with your sentiment, I don't think 1.5x for 48 hours for being on call over a weekend is a sensible or reasonable ask.
Personally I'd be happy to manage/curtail the occasional weekend's social activity for 2 days pay (or time in lieu), at least as long as it's not as frequent as every month. While almost 2 weeks pay for being on call (and potentially never actually paged) would be nice, it's a kind of insane ask that just sends the wrong message in my opinion. If you don't want to do on call, just say so. Don't risk being mis interpreted as being a money-grubbing mercenary by pretending you'd be happy to do it for a high enough price that it would be totally impractical for most businesses to pay.
(If you came to me with the demand for 72 hours pay for being on call over a weekend, I'd advertise your position with a "regular 1 web in 6 on call" in the job description explaining you get 2 days pay for being on call for a weekend, then PIP you out for being a jerk as soon as I could. You're looking a lot like either a money-grubbing mercenary, or a spectacularly bad communicator.)