Lowering the cost of mining Bitcoin is not a positive impact on the currency. This is because it will increase the amount of Bitcoin in circulation greatly therefore causing the price of the crypto currency to drop which will result in great loss for those hodling Bitcoin before the incident. The currency has to be difficult to mine in other to protect it's value.
This is my idea
No such thing can happen, there is something called "difficulty" in mining, it doesn't matter how cheap it becomes to mine bitcoin or how many people mine it, the protocol will always keep the average block time at 10 minutes, ya not 100% adjusted but overall perfectly aligned.
I don't think it's wise to buy all 30 ASIC units from Bitmain you can get cheaper from Canaan units if you are planning to lower the cost.
Here is a fair warning, the recent gears made by Canaan are of very low quality, it's probably why they had 80% drop in revenue in Q4 last year, it's either Bitmain or Whatsminer, the former for better efficiency, the latter for better quality.
And the main part of lowering the cost is the Electricity rate but I think you can only get cheap power in 3rd world country.
The United States has 50% or more of the current hashrate, and it doesn't fall into the 3rd world country (I hate that term anyway).
OP, the first thing you need to check is the power rate, anything above 6 cents is risky, 7 cents is maybe doable but you will need a lot of luck, depending on your power cost, you pick the right piece of gear, where do you buy the miners from also matters, which country do you come from? if you are in the U.S., it's cheaper to buy miners from other resellers than to buy them straight from the factory.