I've long heard of Grumman so when I saw their food truck I was initially excited. Thus, my experience below is limited only to their food truck.
I don't recall EVER paying more than $3 for a taco but I did so by paying $7 for their Bahn-Mi taco. I expected a huge orgasmic tasting taco for that price but what I was served was smallish sized taco that I'd be more than happy to pay $3 or so for. The toppings were fresh and tasty and overall I liked it but I've had better... I truly felt the price was far too exaggerated, even by food truck standards. I can probably eat 4-5 of these but no way I'd pay this kind of price-tag. I had to fill myself up with left over fries from the very generous servings my friends got from the other food truck.
Furthermore, I also took their juice, I forgot the name but tasted somewhat like cranberry. It was served in a bag (with a straw) which made trying to eat your taco while holding a round plastic bag somewhat challenging. It was quite tasty however. I'd suggest investing in another container or a plastic bag that has a square bottom.
I feel like giving this place a 2 star rating somewhat unfair (the food truck once again) but at this point, they're just exaggerating their prices and they need to be called out for. The food is good but the value is clearly not. There's just no sense paying $7 for a taco. Hipster or not.