How can I explain this concept to my mom?

She's so annoying with her "You can make it cheaper". I want a paintball gun for my birthday and it's quite expensive for the order with a mask and a loader (Planet Eclipse Etek 3), so I agreed to pay some of it (A lot approx $260 which is bs since it's my birthday) but anyways, how can I explain to her that a more expensive gun is constructed better and not gonna be a pain to maintain, and won't have errors as much? She thinks a cheaper gun is gonna be exactly the same and it makes me angry to the point I literally wanna put a gun in her mouth (I won't do that though). So how can I explain this to her? Basically she said "A cheaper gun is still gonna have the same amount of mechanical errors it's gonna be the same gun but cheaper". She doesn't understand the difference between the car world and paintball world. Since almost every car on the street is just as good (unless it's a sh*tty beat up 1995 chevy that's clearly been in at least 4 wrecks and is rusted from the inside out with the rear view and AC missing)