I bet you don't regret it even for that price. Guys that have this phone should do this mod. It is very easy.
Take some thin foam 1/4 thick. Very important that it is not thicker than 1/4 inch. I am using flooring insulation foams. Cut out roughly the diameter of the cups. unstick the pads from the base of the cups by running your fingers around the bottom of the pads to separate the pad from base of the cup, it is stuck on there with a bit of glue. Then put the foams underneath.
Will bring the phones to a new level and it certainly will not sound like your garden variety $200 phone.
Exactly what kind of sonic effect with this have?