Uh, actually the OP is correct.
You need 2,400 shards + the drop from Tyth to get Tyth's Power Relay.
Assuming that each of the 5 bosses requires 2400 shards that's 12,000 shards total.
However, I suspect that you don't need the 5 Power Relays on the same toon, merely in the same group. So 5 of 8/16 players need to spend 2,400 shards. Given that the power relays are useless until the 5th boss is released, we've got over 5 months to get 2,400 shards - plenty of time.