Build with plywood and laminated floor finish, i think should be around 3k+

Wood base platform is hollow, so there should have a sound when u step harder. If really want to make the no sound at all, if the location is possible, then u can use cement base as a platform, then lay with laminated floor board with under-lay then that will really no sound at all just like normal floor.

Actually by using plywood, there will having a same problem when you remove the platform, coz there will leave a mark on the floow while u see diff color for your existing floor tiles, and also usually they will use maxbone to fix the plywood, so that will leave on the floor while you remove.