Dropships & Jumpships listed a 30,000 C-Bill price for a Reentry Kit. I'm not sure a price has been listed anywhere else.
The book seemed to assume that the metal and ceramic pod would be retrieved after use and the foam and ceramic cocoon would be destroyed by friction, since it also listed a 5,000 C-Bill refurbishing price.
"The one-ton reentry kit is designed to be used by Battlemechs that are dropped from orbit. These kits consist of a ceramic and metal capsul (the DropPod) and a spun foam and ceramic structure (the cocoon). As the `Mech hits the atmosphere, the DropPod absorbs the great amount of friction generated. After a time, timed explosions break the DropPod into five sections (which will confuse ground-based observers). Then, the cocoon absorbs the friction, shredding away in the process and adding to the radar-reflective debris surrounding the `Mech."