I was playing some Twisted Treeline games with Robb and Snuggles last week and we had a bit of a discussion about the crystalline flask. It was changed in a recent patch to cost more and return more health/mana, and I liked the new version more. Snuggles used to buy the old version and won't buy the new one. I didn't really know what had changed, so I wanted to take a look and see what's really going here.
Old flask - cost 225, 3 hits of 100 health, 40 mana over 10 seconds.
New flask - cost 345, 3 hits of 120 health, 60 mana over 12 seconds.
The old flask was definitely more cost efficient, and was the same amount of healing as 2 healing potions and 1.2 mana potions. So each time out to lane, assuming you could use all of the health/mana, would be worth 112 gold. So it would break even in pretty much two trips to lane. The new flask is worth 2.4 healing potions and 1.8 mana potions. So it breaks even at 2.3 trips back to lane. The old flask broke even faster, but the new flask was worth a little more every time you go back to base. They're both worth the same amount of health per second, so spamming it in combat is equivalent for the first 30 seconds of the fight (which is really all that matters).
So, looking at the numbers, the flask definitely seems to have gotten worse. I think, however, that I was undervaluing it in the past and not overvaluing it now. It's still worth 2 ruby crystals of health in a prolonged fight (which most early game lane matches are) which is a really fantastic value. I should have been buying it more often back in the day, and do think it's right to buy it now. However, you really need to be able to make use of the extra mana from the new flask as it makes up a pretty significant amount of the value for the item. So it feels like anyone who would consider buying early mana potions or mana regen items is probably well suited to grabbing a flask. Anyone who doesn't really want the mana should probably just buy a couple healing potions and move on with their life.