Good question: Lets talk about some set up for the new guys getting in

1.100 aged account $200 possibly less .
2. 100 accounts to 20k naturally plus with warm up time ( must do ! ) will take 10 months possibly longer to get to 20k followers ( genuine followers ) possibly shorter depending on niche and strategy so you need to factor in some things.
3. So depending on software that could vary in cost. Lets just say you buy software that is 1 time fee $100 so your in $300 so far Not counting hours learning ( whats your time worth??)
4. Now you need VPS decent to run 100 accounts your in $20 a month x 10 months =$200
5. Proxies what type will you use? IPV4 IPV6 Residential or Mobile (advice :skip the IPV6 I know the low cost is tempting but do not do it) Lets say you want to go on the cheaper side of the spectrum and you go with IPV4 will you use 1 proxy per decent proxy per unit is $2 per and that is each month so $200 a month.
5a. But lets say your a risky kind of guy/gal so you do 2 accounts per proxy cut your proxy cost in 1/2 to $100 a month
5b. But now we have to deal with PV now we have 0.2 per PV this can rack up..
Now your in hours of time and $500
6. Now lets talk about payout per opt in or sign up or sale this can vary
7. Possibly you do shout outs or account rentals or bio link rentals.
8. Possibly to make this high of a profit you should have your own products digital not physical.
So the long story short to make 20k from 100 accounts is possible and could happen. Depending on the product or the stance you will take. But from my experience you will need a lot more accounts for CPA to make that $$$
And the accounts will be a lot larger to sell shouts and DM space etc etc...
So anyone going to jump in first be patient hitting 20k a month is in my opinion not very realistic ( at first ) also doing IG properly will take a lot of upfront investment and time.
Start small with 20 accounts than grow adding 20 more etc..etc..
We see countless journeys with people thinking to big at first and failing know when starting its a long road and there is a lot to learn and so up front investment. Factor these things in and possibly think about using a service to help the process- ( be on the look out for mine-
So,
@Teofil to hit your goal you need your own product in my opinion or a lot more accounts.
Hope this helps guys