No doubt, every penny counts and $3k is not chump change regardless of what your income bracket is. But this happens on almost everything we buy, from $10 books on Amazon to $500k homes. The vast majority of the time, the price it what it is when you buy it, and if it was worth it to you then, then be happy! No regular auto dealership is going to retroactively go back and refund $3k on every Volvo it sold last week just because someone came in and negotiated a $3k discount on the one they just bought today. No auto dealership is going to retroactively apply a new manufacturer incentive to prior sales.
And if it's resale value you're worried about, take comfort in the fact that Tesla is crushing the competition in that area too:
Tesla Model 3 retains almost 90% of its value over 3 years, study shows - Electrek It may be premature to suggest that a lower MSRP affects long-term value. The legacy car industry had fixed MSRP and yes, that could be tied to future residual value. But Tesla has a new take on this too... they don't have fixed MSRP, just like they don't have fixed model year iterations (though they do now in name). The market hasn't caught up yet it terms of how do deal with that calculation for a car whose MSRP is variable.
In the scheme of life is $3k worth getting bent out of shape about? Life's too short, enjoy your new car!