I think the general public are now domain-aware enough to recognize that the reason you don’t have your exact-match domain is because you couldn’t afford it. I do think Tesla would be better served owning Tesla.com as this would increase the perceived value of the brand. Compare to GM.com, Ford.com etc. As far as adding modifiers (additional words) to your brand in order to acquire the domain name: That you have to add a modifier implies higher word value in your brand itself, which implies more competition with trademarks. As a young bootstrap startup you may be better off adding the ly or io to your name because your trip to the trademark office will be that much easier as well.
It’s not the end of the road for .com, not by a long shot and Elon Musk’s Tesla has shown the way. Tesla, a pure Internet play, was unable to obtain Tesla.com. The herd in the world of startups would have insisted Mr. Musk could not go forward with the name Tesla without owning Tesla.com – they would have demanded it be changed to something like Electicarly.com or whatever domain was registrable. Tesla correctly went forward with a modified domain, TeslaMotors.com. In this case the modifier “motors” was chosen, but the possible modifiers are nearly infinite. Here is a list of the 5,000 most common .com modifiers.