User blog comment:Krufix/Last Whisper - When to get?/@comment-4990650-20121106080756

lets say u have IE at lvl 10 means ~ 80 +80 IE+15 runes+8 mastery+10 doran= 192 and 0.87 AS. and 2.3k more free.

against lvl 10 enemies ~ 46 AR+ 14 runes = 60, 10% arpen master = 56.

LW=40 AD and 40% ARpen= 232 on 34 AR = 174 damage.

BT= 292 AD on 56 AR =186 thou you cant buy BT with 2.3 k and it is a fully stacked one. a none stacked is 252 on 56 = 161.

PD =1.34 AS = 257 dps on 56 AR = 164.6 dps.

LW = 0.87 as = 202 dps on 34 AR = 151 dps.

PD cost ~ 400 more and has 30% crit which cant be calculated.

Some champs style is about auto attack (which will crit) (ashe..) other doesnt really attack much (Graves..).

so check if ur champ synergy well with crit from some few 1st lvl to buy PD and buy LW if they all have more than 60 AR (which likely be the case)