1) Give a quantitative comparison to determine the correct values.
How can I take the reusable ability of this card into calculation ?
Unstable Hourglass gives card advantage over Unstable Gas
BUT, Unstable Hourglass also leads to repeated draws, clogging your deck.
Neglect the reusable aspect, considering only one card :
For
Unstable Hourglass : cost = 5
+ 1 card + 1 turn = 7
Efficiency = 7 /13 = 0.54 cost for each point of damage to opponent
For
unstable gas : cost = 6
+ 1
+ 1 card + 1 turn = 9
Efficiency = 9 / 20 = 0.45 cost for each point of damage to opponent
Well...UH is currently weaker than UG....