Each new creature makes Mana Echoes add for every creature you control that shares a type with it, so the loop costs less the more of them you have. Each colored mana takes of the through the combo's mana converter.
Mana to start
Each loop costs
Loops before it pays for itself
2
Your mana, step by step
100050100150200250
To start: To start: 0
Pay : 1 leftPay : 1 left1
Mana Echoes adds 5: 6Mana Echoes adds 5: 62
Pay : 0 leftPay : 0 left3
Mana Echoes adds 9: 9Mana Echoes adds 9: 94
Pay : 2 leftPay : 2 left5
Mana Echoes adds 13: 15Mana Echoes adds 13: 156
Pay : 8 leftPay : 8 left7
Mana Echoes adds 17: 25Mana Echoes adds 17: 258
Pay : 18 leftPay : 18 left9
Mana Echoes adds 21: 39Mana Echoes adds 21: 3910
Pay : 32 leftPay : 32 left11
Mana Echoes adds 25: 57Mana Echoes adds 25: 5712
Pay : 50 leftPay : 50 left13
Mana Echoes adds 29: 79Mana Echoes adds 29: 7914
Pay : 72 leftPay : 72 left15
Mana Echoes adds 33: 105Mana Echoes adds 33: 10516
Pay : 98 leftPay : 98 left17
Mana Echoes adds 37: 135Mana Echoes adds 37: 13518
Pay : 128 leftPay : 128 left19
Mana Echoes adds 41: 169Mana Echoes adds 41: 16920
Pay : 162 leftPay : 162 left21
Mana Echoes adds 45: 207Mana Echoes adds 45: 20722
Pay : 200 leftPay : 200 left23
Mana Echoes adds 49: 249Mana Echoes adds 49: 24924