There is no comparable product to the Model 3, an all electric luxury sedan with a range of 200 miles at a base cost of $35,000. Other than the Bolt the cars you mention are not all electric and the Bolt is not a luxury sedan. The 2017 Volt with an electric range of less than 45 has a higher base price of $40-$45k. The Volt and Bolt are not sold in most states and are only available mainly in California and Northeast Corridor. There are non sold within 1000 miles of my location.
OK, I am going to have to call you on this, because it isn't true and it drives me nuts when people spread FUD about the Volt - the Volt is available nationwide. There are several 2017 Volts for sale at David Maus Chevrolet which is way closer than 1000 miles to you. There is always at least 1 Chevy dealer in every metro area who ends up specializing in Volts.
Back to the topic at hand - how do we know the Model 3 will be a luxury vehicle? People buying the $35,000 model may very well cross-shop it with a Bolt, and I will bet the Bolt will probably come equipped with more features for the same amount of money (and there is the fact that no one pays MSRP for a GM car, so it will probably be priced exactly the same as the Tesla in the real world).
So if someone is looking at the base model and needs the tax credit, there is a Bolt that will be available earlier than the 3 and they might decide to jump on that and guarantee themselves the tax credit vs waiting for the base model 3, which will most likely not come with the credit. So I would say the Bolt IS a comparable vehicle when we are talking about the base models.