Sure you can get a pack of cheap microfibre cloths but they won't work the same way.One cloth for $25? I can get a whole pack of microfibre cloths on Amazon for that.
Is the Apple cloth overpriced? Sure but it is also unique and made specifically for Apple Laptop screens.
I have bought a variety of microfiber cloths and some leave a lot of lint behind. Some work great but any cloth that is of high quality is over $10 and some cost about the same as the Apple Cloth.
Personally when spending as much as I do for Apple products I would rather spend a little more so I don't damage my devices prematurely.