I'll only jump into this once, because trying to give a rationale perspective on these topics here is like pissing into the wind.
Yes, there are "appraisal companies" out there that will give you a write up. But they're the equivalent of ambulance chasers. They use nothing but a pre-made template and plug your car in and pull a number out their rear ends. Trust me, I've got dozens of examples of them, and they're all the same. If you want to pay someone $150 for that, go for it. Don't expect to recoup that money, or have it mean a lot to the insurance company...or a judge.
Every company does handle DV differently, but the premise is the same. It's NOT based on the dollar value of the damage. Here's why...if I damage the headlights and grill on a 2014 Mitsubishi Mirage, what's the repair bill? $1000 maybe. If I do the same exact thing to a 2014 Mercedes S class, what's that damage? $5000 or more. Same damage. Most companies base diminished value on severity of damage (judged by the repair estimate line items), age, mileage, condition and pre-loss value of the car.
As ddavid said, most states don't even recognize a 1st party diminished value claim. In other words, if you were to claim DV against your own policy, unless you were in GA, KS or one or two other states, you're not getting it. It's excluded on your policy. If you're claiming it against the other driver, all 50 states recognize the right to make a claim, but there is no case law out there that specifies how that claim must be settled. I researched this just a few months ago. It's 100% subjective. I could argue that as long as the car was repaired properly, there is no DV. If it wasn't repaired properly, that's a matter between you and your body shop.
Last question I'd ask you is what amount were you expecting? I often hear people say their $20,000 car is now worth $4000 less because of an accident. Those reports from the "experts" will say that. If that's accurate, the car is now worth $16,000. Take a peek on Autotrader, Cars.com, etc...go find a car that's just like yours that has a Carfax report of an accident and is listed for $16k. I'll bet you won't find it. Time and again, I find examples of cars with Carfax accidents being sold for the same price as ones with "clean" Carfax reports.
Oh, and on that note, those experts you hire will cite dealer trade in value to try to support their argument. Even court cases (for first party claims) have agreed that when considering diminished value, it's based on retail value...not trade in.
I'm not saying I never pay DV claims. In fact, I'd say about 70-75% of claims made have a payment offer made. But the amount listed by OP sounds about spot on for cosmetic damage (based on his description).
<<<< drops the mic and walks out.