A dedicated will only make a difference to the sound of your turntable and if you have a suspended floor then the TT is better off on a wall shelf anyway. The performance of solid state devices is unaffected by vibration orders of magnitude greater than it will experience sat in domestic room. There's zero benefit to be had from any anti-vibration/isolating/ coupling treatment.
And as you have noticed the price of hi-fi racks is utterly ludicrous compared to the material value.