Earlier quoted context omitted.
What's the cost? It was 36MB originally and it has been reduced to 1MB as a temporary measure to limit spam.
The cost is that larger blocks have difficulty crossing the great firewall of china and mining is already centralized there. I have seen this myself with a production blockchain and blocks that were less than 1mb. Increasing the size increases this effect and gives Chinese miners and artificial advantage. Plus there's no congestion on the network right now. There's not a scaling problem. It was spam. Further, segwit…
Ironically, this has actually become a real Byzantine Generals problem. Guess Bitcoin can't actually solve that problem in the real world.
From what I understand, China isn't too keen on the whole endeavor since it circumvents their (stringent) capital controls. What happens if they turn the baleful eye of their deep packet inspection onto the Bitcoin network? (serious question)
(Background for those who don't know: encryption/etc don't work against the Great Firewall, it knows what a given type of connection "looks like" in terms of packets/activity, so it can identify (eg) a VPN session even if it's "wrapped" or "tunneled" across some other protocol. They use a massive amount of machine learning hardware to profile connections in realtime to pick out "suspicious" activity and those connections will be dropped after a few moments. It's not impossible to run arbitrary connections through the firewall but it's very difficult and getting harder all the time.)