Smaller sets mean less content.
They've been padding the sets with way too much filler for some time now. This is partially because the game is 15 years old. Over time it becomes harder and harder to stay fresh.
More importantly, for the past 2-3 years, they've been slowly pushing for 4 sets a year instead of three. This has blown up in their faces, because LESS packs are being opened, driving up the prices of Type 2 rares to ludicrous levels and semi-new players (i.e. their core market: people who've been playing for 1-3 years) were too financially fatigued to keep up.
That's not just WotC selling a line, that IS what was happening. Less Morningtide (or whatever) is opened, so dumbshit like Mutavault or Bitterblossom goes for $35, I mean, that is some serious fucking cracksmokery. Lorwyn block was WotC reaching the saturation point. And then putting out more. When awful shit like Figure of Destiny or Stillmoon Cavalier reaches the prices they have, it's indicative of a broken supply-and-demand model.
I for one welcome smaller sets less often.
Mythic rares are intended to encourage the buying of packs over singles.
Uh, the effect in real life is pretty much the opposite. If I want a Tezzeret, I'll let the dealer open $1000 worth of product and then happily pay the dealer $25 for the card. Only crackheaded retards open packs looking for a given rare - doing this with mythic rares is precisely 1.7 times as stupid.
Replacing a common with a land in each pack means they don't have to print as much to make the same money.
It's the same number of cards. They could print boosters with 15 Black Lotueses in them and it would cost the same. If anything, the need to sub in another print sheet and recalibrate the sorting would INCREASE printing costs, not decrease them (which is why lands were cut from packs anyway: simplicity in printing).