I think it's likely margins will be thin at best on base models. However, that can be written into marketing expense in the same way Supercharging has been. If they make the base 3 attractive enough to bring in customers, but not attractive enough to keep them from upgrading, it's precisely that. This is a well known and used tactic - it's called a loss leader.
Loss leader and losing money on each sale is the same thing. One sounds nicer than the other.
We have a lot of geniuses here that think you can outprofit GM when
1.) Cost of inputs higher.
2.) Unit volume low.
3.) Niche market.
Tesla is trying to solve all 3 and I am sure GM made the Bolt as cheap as it possibly could. If the 3 matches the Bolt in price and no one buys 8-10k worth of options, does anyone seriously think Tesla made more money than GM? I'd put money on this wager.
We can approximate if my wager is correct if there are limited Model 3 design options and there are many software unlockables.