Internal bra - how much does the material usually cost?

For such a large implant, you will need the high profile or it may not fit on your frame. I would suggest going down in size, for 600 will be very heavy on your frame and tissue and stretch and thin your tissue.

Yes, your pockets can be tightened and move your implants back up higher. However, your tissue is not supporting the weight of these implants now, so you need to go smaller. You may still need extra support with mesh as an internal bra. Please do not go larger.

You probably don't need the full lift. One implant needs the lateral pocket tighten since it sits too far laterally. The other implant needs the inferior pocket tightened which is causing that nipple to push up higher. Do not go larger and consider going somewhat smaller for a lighter implant.