Three things:
1) You buy the before mentioned shells of a frozen food manufacturer and used again -> products I do not like.
2) You buy the shells from another manufacturer. Have in our three shops found no matching or had when holes -> for few euros I invest not my precious spare time when I already treat myself to a several hundred-euro Grill.
3) It uses the existing metal shell of Weber grills or sets at least with aluminum foil -> awkward to clean or Saurei as always bib.
Conclusion:
I invest the 8, - for the overpriced dishes, fill it before grilling always a few centimeters of water to come thus to the ten-pack certainly over the next 2-3 years :-).