It is a lot more feasible with 6 cents that's for sure, this rate is the average for the industry and thus your chances of making a profit increased by a few orders of magnitude, what I don't like about this business plan is the S19 pro part, it's way overpriced and since you can get 6 cents per Kwh that is sort of an edge which you have to make use of, people with free power buy T9+ which is about 10$/th, those with 1-2 cents buy S9s which costs about 14$/th today, so paying $10,000 for S19 pro at a cost of $90/th is without a doubt a terrible idea, let's just make a simple assumption that whatever the ROI that shows now is going to be shifted by 50%.

S19 pro ROI = 10,000/ 770 = 13 months * 1.5 = 19 months > terrible.
M20s (used) ROI =3500 / 390 = 9 months * 1.5 = 13 months > bad.
T17 (used)  ROI = 1700/ 250 = 6.5 months *1.5 = 10 months > not so bad.

*These are based on 6 cents Khw, prices in China + 300-500$ for shipping and duties, the T17 is a terrible gear, it was just there in the reseller list I got recently so I used it

But you get the point I suppose.

Of course, you can go to as low as S9, ROI will be $300/60 = 5 months * 1.5 = 7.5 months, but then it will be a bit risky because if the price drops a bit of difficulty goes up a bit that 60 bucks will disappear and you will start losing, unlike the S19 pro which has a ton of room for profit, these are some of things you need to consider, there is no right or wrong about it, it all depends on your risk management.

Other important factors such as failure are also important, investing 10k in a single gear means that if one hash board is dead, you lose about 3k worth, investing in 3k gear you only lose 1k worth, of course investing in 10k gears means less work and easier management, but everything comes at a cost.

Also, the availability of mining gears in your country is very important, for example, if you want to be in the mid-range risk and go with say M20s, but then find out it will cost you 7k instead of 3.5k, then the S19 pro will be a lot better, if you get lucky and find S9i/S9js for 200$ then ROI is only 5 months and thus might be worth taking the risk, I can't tell you what gears to buy ( don't buy any 17 series from Bitmain because they have high failure rate).

The 1.5 factor isn't something you can count on, it's just a speculation, if your risk tolerance is strict, make it a factor of 2, if you are a risk-taker, you can just work with a factor of 1, there is really no perfect model that fits everyone, I can't tell you what to buy and when to buy, but I hope I gave you the key points which you need to consider before entering the business.