Based in TPE, and I also received the same message today, titled "Life’s a beach" with a sunny beach house photo (doesn't work well with the season though).
I checked their website and it's indeed 75% bonus, ie.buy 4,000 mile for EUR110, and you get another 3,000 miles (7,000 miles total).
Can go all the way up to EUR2,750 for 100,000 + 75,000 miles. Which is nearly a Europe-Asia round trip Business Class award ticket?
Is it worth it?
I haven't checked fares on CI from TPE to Europe but I spent roughly that amount for a R/T from Europe to Japan with a stop-over in TPE. The trip will result in ~30k miles & 100-odd XP. So...I'd say no for the money as you could get something more than just a flight for the same price.
EDIT: Sorry, it was more like €2,300