Very few people can accurately judge the altitude of aircraft flying by. Maybe you're that one-in-a-million who can. Or maybe you're just like almost everyone else and that plane was really at 500'.
As an airplane owner and lifelong pilot myself, I can tell you that other than operations approaching and departing airports, an aircraft flying as low as you seem to think you're seeing is exceedingly rare (IME, other than at an airport or an airshow, in over 60 years of looking up at every airplane that has ever flown past me, all over the country and beyond, I don't think I've ever seen one at the altitude you claim to see them at regularly - except for a couple of F-16s running down remote valleys in Idaho, and seaplanes scud-running over water in Alaska). Pilots of crewed aircraft just don't do that, because it's incredibly stupid and they don't want to die.
At just 250 feet, you should be able to see the expression on the pilot's face, see whether they're wearing sunglasses or not, see if they have facial hair, and other pretty small details. At 250', if the pilot flipped you the bird as he went by, you would be able to see his individual fingers (and see him smile at you).
My guess would be that the aircraft you are seeing are actually at or above 500' AGL. Even at 500', it's startling to see an airplane go by so "close up" and almost everyone has the same reaction: "Wow, THAT was LOW!"
BTW, the altitude data that's displayed on FlightAware and similar sites is not accurate - not at all. It can be and often is wildly misleading. The "150 foot" Southwest jet inbound to land in Tampa that inspired so much pearl-clutching online from people who don't know chit about airplanes is just one example. That plane was not anywhere near that low (if it was, impossible-too-ignore and very loud ground proximity warnings would be constantly blaring in the cockpit; no such alarms went off because the plane was not dangerously low).