So I'd like to share some data points that I've been tracking for some time. The numbers I have are in the ballpark of what sneekypants listed but I tracked my data based on the specific gear. The four gears that I tracked were Mk 5 Athakam Medpac (Gold Gear) DS 9F, Stun Guns DS 8B, Stun Cuffs LS 7D and Holo Projectors LS 6A. Here are my findings and you can draw whatever conclusions you want from them.
Medpac
22 gained out of 133
Drop Rate - 16.54%
Energy Required for 50 - 3023
Cost - 1259.47 crystals (50 crystal refreshes)
Stun Guns
145 gained out of 624
Drop Rate - 23.24%
Energy Required for 50 - 2152
Cost - 896.55 crystals (50 crystals refreshes)
Stun Cuffs
155 gained out of 839
Drop Rate - 18.47%
Energy Require for 50 - 2706
Cost - 1127.69 crystals (50 crystals refreshes)
Holo Projectors
125 gained out of 514
Drop Rate - 24.32%
Energy Required for 20 - 658
Cost - 274.13 crystals (50 crystals refreshes)
So considering that Stun Guns cost 1274 for 50 salvage, Stun Cuffs at 1400 for 50 and Holo projectors are 300 for 20 in shipments, the data points I drew seemed on par with the drop rates being a little lower than the cost in shipments. Gold gear on the other hand is outrageously priced and is much better being purchased but that piece I had the fewest sims because I quickly drew the conclusion it was a waste of time to try to farm. The same Medpac goes for 750.