This is intentional.* Cells have always been consumables, and no recipe or machine that accepts stuff in cells returns the cells.
I agree that it's expensive. I don't play with GregTech partly for that reason, though now that Greg is involved in IC2 development, "expensive" is the name of the game (er, mod).
If you're playing on your own world (rather than someone else's server), a way around this is to modify the recipes. You can do this three ways:
- Disabling GregTech. (Not an option if you like the other GT changes/items/blocks.)
- Change the GregTech config to not use the expensive cell recipe.
- Use an external mod to alter recipes.
For (3), modifying recipes, I use the excellent MineTweaker mod, which can modify all crafting and furnace recipes including those added by mods, and has recently added limited support for IC2 machine recipes (macerator recipes, etc.).
You can use MineTweaker to change the number of tin cells crafted (I like the MC1.4.7-era recipe myself: 4 tin ingots = 16 cells; but you've got lots of options), which makes using them up hurt a lot less. Being able to return crafting items to the grid (like buckets do in vanilla) is on the ToDo list for MineTweaker, but it's not implemented yet as far as I'm aware.
* Though given that this iteration of IC2 is still under heavy development, the cost balance may not be intentional and might get changed in the future. Then again: GregTech, so expensive is very likely on purpose.