Most of the time in RPG's magical staffs are tipped with some kind of crystal in them. These crystals amplify your mage's magical attack. The staff itself (not the crystal), also contribute to this multiplicative property. So a better
better staff could be made of a finer crystal and/or finer material.
Adding raw magic stat to your mage doesn't really make sense much. Instead, think of it like this. Magical staffs doesn't directly add
add magic power to your mage. But amplify
amplify (multiply) your mage's base magic power.
For instance, instead of a staff adding +14 magic power
$+14 \text{ magic power}$, what happens under the hood is that the staff grants you ×1.14 magic power
$×1.14 \text{ magic power}$ (assuming your magical damage is 100) and the multiplier scales down as your magic gets stronger to maintain the static value of 14
$14$.
In real life, when you lift a 1kg dumbell everyday, eventually this would feel lighter. But it's still 1kg dumbell. The analogy is like that. So what seems to be a strong staff (+14 magic) doesn't really feel that strong anymore when you have higher base magic power.
Or you could make it so, that the staff's crystals+materials have some kind of "cap" to make your magical output a static 14
$14$.
You can experiment around this idea but the gist is that the staff is a conductor of your magical energy and it amplifies instead of working like a "sharper sword".
If lightning travels through a rusty metal, or a sharp metal, the output would probably be the same. But if a lightning (magic power) travels through a metal (fancy staff) versus a rubber or weaker material (poor staff) then the power gap would be much more significant.