Top tip
Always ask what cat washcoat weight is
A 5-gram washcoat will get through an MOT, but due to it being an entropic surface coating it degrades with use - so you have to wonder how many times.
The main cost element is in the precious metal coating, the greater the load the higher the cost.
If you can't get an answer or they don't know walk away.
FYI the OEM cat will typically have a 60gram coating.
Cheers'
Nige