Long time lurker, first time poster. I just drive a lowly Kia Soul EV.
Annyyyyway I've been chewing over the Model 3 numbers for a while and I thought it was borderline implausible that TM would be able to deliver a $35,000 ~55 kWh car and make any money on it right up until the Q1 call.
Elon guided that once Gigafactory cells are in production that they anticipate a 20% gross margin on stationary storage. This means that since they're selling stationary for $250/kWh that TM has a BOM price of $200/kWh or lower effective Q2 2016. I presume it will drop slightly by the time Q4 2017 rolls around.
This implies a cost of ~$11,000 for the pack in the Model 3. Starting at $35,000 MSRP and backing out TM's 25% gross margin that leaves us $26,250 to play with. Subtract the battery pack and that leaves $15,250. The most expensive parts of a car outside of powertrain are seats, glass, and crash pyrotechnics. Even so, I can say with relative confidence that it costs much less than $15,250 in parts and labor to assemble a modern automobile. Furthermore I expect Supercharging to be a $2,000 option which the vast majority of 3s will be equipped with, effectively bumping up the MSRP nearly 6%.
Stamp the 3 out of steel, equip it with less flashy rims, brightwork, and lighting, make everything optional (a la BMW), and there should be no issue in TM sourcing materials and assembling a compact/midsize sedan for $15,250 with a 25% gross margin.
As far as timeline and potential delays, I think Elon's got this sorted by now. Besides the chassis stampings and crash testing, there's not a lot left to do. Seats, pyrotechnics, glass, steering column, and lighting will all be from suppliers. The OBC will be the same as the S/X/Supercharger, the mobile connector is done, the cooling systems will be largely carryover, vehicle software is likely to be similar, etc. If it's front drive, the Ds/B-Classes/RAVs have taken care of front drive engineering and packaging work, if it's rear drive then it's drop in.
As an armchair quarterback I think the Model 3 will be on time and at or near the promised MSRP.