I appreciate that you’re willing to do the numbers for those who cannot or will not for themselves, but I venture to offer a differing viewpoint. The epic shard and rare wrench should really be compared to zero cost versions of themselves.
In the previous assessment, the player spends 3004 on gear, and gives up his/her entire loadout. With a free shard generator (+2.1 shards/sec) and a free wrench (-21% buildable cost,) the player can upgrade three turrets to maximum
1200 * .79 = 948 * 3 = 2844 < 3004
before he/she would be able to finish paying for the more expensive set, and they both generate shards at the same rate. The free version gives the player shard regen right away, before he/she even leaves the starting room, and there is an open gear slot for something else. Having the shard regen from the get go isn’t gamebreaking, but neither is the extra 14% buildable cost reduction that actually costs 1050 to activate.
Comparing just these two gear pieces to each other, each fully upgraded turret saves
1200 * .14 = 168 shards
Now for this one piece of gear, we’re looking at 1050 cost versus a saved value of 168 shards per full turret upgrade.
This means the player will actually have to buy
1050 % 168 = 6.25
more than 6 turrets before the epic shard generator saves more than its cost to activate.
But before the player can start spending, he/she first must save 1050, which is also before he/she starts generating his/her own shards. Given that the large shards don’t spawn for the first two minutes, it is very unlikely the player will acquire 1050 shards before two minutes and thirty seconds have passed, so the free shard generator earns you at least
2.1 * 150 seconds = 315 shards
more than the full cost version.
With the free shard generator (and the rest of the full gearset,) the cost to fully upgrade a turret is
.21 + .14 = .35 saved (65% initial cost,) + .14 = .49 saved (51% cost for 2nd and 3rd tier)
300 * .65 = 195
400 * .51 = 204
500 * .51 = 255
195 + 204 + 255 = 654
Total gearset cost being
0 + 924 + 1050 = 1974
Whether or not the other pieces of gear are worth it really depends on how long the match goes, but here we’ll show the cost for one to eight turrets for each gearset
1 * 468 = 468 + 3004 (cost of gear) = 3472.
2 * 468 = 936 + 3004 (cost of gear) = 3940.
3 * 468 = 1404 + 3004 (cost of gear) = 4408.
4 * 468 = 1872 + 3004 (cost of gear) = 4876.
5 * 468 = 2340 + 3004 (cost of gear) = 5344.
6 * 468 = 2808 + 3004 (cost of gear) = 5812.
7 * 468 = 3276 + 3004 (cost of gear) = 6280.
8 * 468 = 3744 + 3004 (cost of gear) = 6748.
versus (with free shard generator)
1 * 654 = 654 + 1974 (cost of gear) = 2628
2 * 654 = 1308 + 1974 (cost of gear) = 3282
3 * 654 = 1962 + 1974 (cost of gear) = 3936
4 * 654 = 2616 + 1974 (cost of gear) = 4590
5 * 654 = 3270 + 1974 (cost of gear) = 5244
6 * 654 = 3924 + 1974 (cost of gear) = 5898
7 * 654 = 4578 + 1974 (cost of gear) = 6552
8 * 654 = 5232 + 1974 (cost of gear) = 7206
However, this doesn’t take into account the 315 extra shards the player would earn with the free version before he/she was able to pay for the epic version, so we’ll take that off the total to compare these two on an even footing.
1 * 654 = 654 + 1974 (cost of gear) = 2628 - 315 = 2313
2 * 654 = 1308 + 1974 (cost of gear) = 3282 - 315 = 2967
3 * 654 = 1962 + 1974 (cost of gear) = 3936 - 315 = 3621
4 * 654 = 2616 + 1974 (cost of gear) = 4590 - 315 = 4275
5 * 654 = 3270 + 1974 (cost of gear) = 5244 - 315 = 4929
6 * 654 = 3924 + 1974 (cost of gear) = 5898 - 315 = 5583
7 * 654 = 4578 + 1974 (cost of gear) = 6552 - 315 = 6237
8 * 654 = 5232 + 1974 (cost of gear) = 7206 - 315 = 6891
With the free shard generator, the player can purchase three fully upgraded turrets before another player using the epic version can purchase his second turret. Both versions purchase seven turrets before the epic version starts showing itself as better, and until that point the free version has always been able to purchase turrets much sooner, and thus earn his experience from building (and also, have the benefit of whatever was built,) much sooner into the match.
Based on my recent match history, only Pendles can really be assured of acquiring 6000 shards before the winner is decided. That said, having those buildables up (and that experience earned) earlier goes a long way towards improving your side’s chances of being the winner, so even in that case I feel the free version is better.
tl;dr: If the match goes very long, the epic shard generator is better. If the match is shorter, the free shard generator is better.