Flash had 2500 minerals in the bank and 200 supply since 20:00, had 5 gas expansions, and dug in defence. Towards the end of the game, he still had 3000 minerals and 2500 gas.
The only damage done to him mostly, is plague, or killing science vessels.
But Flash had so many science vessels (he had 12 "attacking" science vessels, 4 spare vessels on 12 o clock,3 spare vessels in his 2 o clock....lol....)
He practically wiped out 3000+ worth of gas units every time he marches forward with his vessels. Even with 7 gas, a zerg can only take this onslaught for at most 5-6 times.
Then look at the cost effectiveness.
People keep saying, ooo, dont build ultra, dont build zerglings, build hydras, blabla.
Look how horrible zergling+hydralisk+lurker+defilers turned out for him.
Every time he pushed into flash's main, the only casuality on flash's side is his MNM, which are ussuly hanging around so that the tanks can murder everything.
Flash almost never lost a single tank whenever he got attacked at his 3 o clock, only plague, however he pulled and repaired every single tank over and over.
Every time flash lost some 500 minerals worth of MNM, his tank murdered 200/200 zerg units worth thousands and thousands of gas. The degree of cost effectiveness of Flash's defence was like killing 5 shuttles filled with reavers with a single marine.
And mind you, flash only used like 10% of his tanks in defence, he had tanks on his 12 o clock, and every expansion had tanks behind turrets.
He also had so many turrets that even guardians dies to them (lol) so i dont see how drop's could have worked, specially considering how 3/3 marines will annihilate any kind of drop play.