Why can’t I unlock the last 6 or so levels on Tiny Death Star

I've been building whenever I can, but I've only built imperial levels when I needed to because of the imperial objective. I decided to follow this strategy as the more non-imperial levels you have, the greater your passive money earned grows. Imperial levels only generate credits when you create all the required items on them, and that requires active play time. So they are non-earners when you aren't playing.

The values for floors don't start according to a formula until you get to floor 12, which costs 12,150. Once you reach that floor, the formula is:

150 * (Floor # - 3) * (Floor # - 3)

So, for floor 12 (which is actually the 10th floor you build) , you'd come up with: 150 * 9 * 9 = 12,150

For floor 83, you'd come up with 150 * 80 * 80 = 960,000

I've verified this formula works for all floors from 12 to 83. Floors 3 through 11 appear to be random in how costs are calculated.

Also, random factoid, the amount of the increase increases by 300 for each level (after 12). So going from 12 (12,150) to 13 (15,000) is a 2,850 increase. Going from 13 (15,000) to 14 (18,150) is a 3,150 increase, which is the 2,850 (from 12->13) + 300.

Going from 14 (18,150) to 15 (21,600) increases by 3,150 + 300 for a total of 3,450.

I'm sure that's just a function of math in the original formula, but I thought it was a neat pattern.

As requested, here is a graph of the costs:

Here are the values for each floor and how long it takes to build:

Floor | Hours | Coins

Floor 1 | N/A | N/A

Floor 2 | N/A | N/A

Floor 3 | N/A | 100

Floor 4 | 0.066 | 200

Floor 5 | 0.1 | 500

Floor 6 | 0.2 | 650

Floor 7 | 0 | 1,000

Floor 8 | 0.5 | 1,650

Floor 9 | 1 | 3,150

Floor 10 | 1.5 | 4,400

Floor 11 | 2 | 8,600

Floor 12 | 2.5 | 12,150

Floor 13 | 3 | 15,000

Floor 14 | 3.5 | 18,150

Floor 15 | 4 | 21,600

Floor 16 | 4.5 | 25,350

Floor 17 | 5 | 29,400

Floor 18 | 5.5 | 33,750

Floor 19 | 6 | 38,400

Floor 20 | 6.5 | 43,350

Floor 21 | 7 | 48,600

Floor 22 | 7.5 | 54,150

Floor 23 | 8 | 60,000

Floor 24 | 8.5 | 66,150

Floor 25 | 9 | 72,600

Floor 26 | 9.5 | 79,350

Floor 27 | 10 | 86,400

Floor 28 | 10.5 | 93,750

Floor 29 | 11 | 101,400

Floor 30 | 11.5 | 109,350

Floor 31 | 12 | 117,600

Floor 32 | 12.5 | 126,150

Floor 33 | 13 | 135,000

Floor 34 | 13.5 | 144,150

Floor 35 | 14 | 153,600

Floor 36 | 14.5 | 163,350

Floor 37 | 15 | 173,400

Floor 38 | 15.5 | 183,750

Floor 39 | 16 | 194,400

Floor 40 | 16.5 | 205,350

Floor 41 | 17 | 216,600

Floor 42 | 17.5 | 228,150

Floor 43 | 18 | 240,000

Floor 44 | 18.5 | 252,150

Floor 45 | 19 | 264,600

Floor 46 | 19.5 | 277,350

Floor 47 | 20 | 290,400

Floor 48 | 20.5 | 303,750

Floor 49 | 21 | 317,400

Floor 50 | 21.5 | 331,350

Floor 51 | 22 | 345,600

Floor 52 | 22.5 | 360,150

Floor 53 | 23 | 375,000

Floor 54 | 23.5 | 390,150

Floor 55 | 24 | 405,600

Floor 56 | 24.5 | 421,350

Floor 57 | 25 | 437,400

Floor 58 | 25.5 | 453,750

Floor 59 | 26 | 470,400

Floor 60 | 26.5 | 487,350

Floor 61 | 27 | 504,600

Floor 62 | 27.5 | 522,150

Floor 63 | 28 | 540,000

Floor 64 | 28.5 | 558,150

Floor 65 | 29 | 576,600

Floor 66 | 29.5 | 595,350

Floor 67 | 30 | 614,400

Floor 68 | 30.5 | 633,750

Floor 69 | 31 | 653,400

Floor 70 | 31.5 | 673,350

Floor 71 | 32 | 693,600

Floor 72 | 32.5 | 714,150

Floor 73 | 33 | 735,000

Floor 74 | 33.5 | 756,150

Floor 75 | 34 | 777,600

Floor 76 | 34.5 | 799,350

Floor 77 | 35 | 821,400

Floor 78 | 35.5 | 843,750

Floor 79 | 36 | 866,400

Floor 80 | 36.5 | 889,350

Floor 81 | 37 | 912,600

Floor 82 | 37.5 | 936,150

Floor 83 | 38 | 960,000