Wave ROM is tricky. You can also read the fine print that 64 MB when converted to 16bit linear ROM.

So, it depends on how good the compression they applied. You could have 100MB sounding worse than 10MB, if they compressed a lot.

Also, it's matter of quality versus, quantity. You could have 10 terrible sounding samples, with lot of looping, or 1 long sample with natural decay occupying same amount of ROM.