Are you wondering whether vegan butter from Becel or Naturli actually gives you a real advantage - or are you mostly paying for marketing? Honestly, I think the answers so far only tell half the story. Yes, production costs more, but the price difference is bigger than the actual production costs would justify. It's also a market phenomenon: these products are still relatively new and target people who are willing to spend more - so the price gets set accordingly. The manufacturers know there's a paying customer base out there.
But here's the more important thing: if you don't live vegan, you're really just paying for a "healthier"-effect that probably doesn't even exist. Vegan butter isn't necessarily healthier than regular butter - both have pretty much the same amount of fat and calories. With some products there are even more emulsifiers and additives in them than in real butter. You'd really need to look at individual nutritional values to see if there's an actual difference for you.
If neither environmental nor ethical reasons really drive you, then you don't need to buy the vegan version. Just get regular butter and save yourself the money - that's not a weakness, that's being honest with yourself. But if the environmental aspect of palm oil in vegan butter worries you, check the ingredients list first.