If you wait until after the declare blockers step, because all combat damage is dealt at once, Kaito won't normally deal combat damage
This is why Dreamscape Artist or Incarnation Technique are handy, as we can dump expensive things like a Spawning Kraken or Thryx, the Sudden Storm , and then grab it out of the graveyard with a Return from Extinction , Stitch Together , Extract from Darkness , or Dead Return
Mishras Factory, unlike Strip Mine, wasnt a staple for one particular type of deck, it was just inserted into almost every type of deck, depending on the builder/player
Because you generally only have a few creatures, since you are focused on just one, it makes you susceptible to attacks from the rest of the players in the game
That said, the card is seeing a vast array of price points depending on its condition, with some going for as little as $21