The sleeve also adds to the initial cost. In cartridge seals it would be silly to build an unbalanced version because the sleeve is always present, but some companies do it any way. The elastomer acts as a natural vibration damper to prevent face chipping and separation. Only the O-Ring version can be used for either vacuum or pressure. The O-ring has the widest selection of materials available and is the most precision elastomer you can purchase.
All elastomers have an upper and lower temperature limit.
The metal bellows seal. All elastomers have been eliminated from the design. Wider range of temperature sealing. Excellent in Cryogenic sealing and most hot fluids with the exception of petroleum products. Higher cost than comparable elastomer sealing.