In the same order.
Display Module - both master/slave - $98 (highly recommended - you only need 1 set of these, not 2)
USB Port & Cable - $30 (recommended - you'll need 2 of these, 1 for each board)
PS12.5 Power Supply - $99 (optional, you can use any 12 VDC supply source including a wall-wart etc. )
LDR3x.V2.1 (must have - 2 boards) - $398
LDR Modules (optional - V2.1 comes with essential 4) - $0
Encoder Module (highly recommended) - $23
IO3 Relay Board (highly recommended - 2 - need one for each board) - $118
Are these the parts and quantities required to build a Balanced Tortuga? I would not want SE inputs or outputs. Of course, enclosure, connectors, wire and remote are needed.