Why do canned Sardines vary in prices?

yea.. there are some that come with olive oil, less salt, extra omega 3, chilli , etc. But for the same number of fish(4pcs) in a Can (425grams) packing, prices could differ from $1.20 to $3.90.
Question :
1) Are there different spieces of sardines (like pink Salmon or Chinook salmon) that makes it cost more?
2) Is price a good guide to nutritional value of canned Sardines? Let alone, all those : less salt, more spicy and olive oil gimmicks?