But that is for a different reason... it's not increased pricing because of increased risk, it's increased pricing because of increased willingness to pay combined with a sense of "more costly must be more valuable".

I would think that risk could be a part of it (or at least risk mitigation)...

If I were a photagrapher, I would likely want to charge more for a wedding then say the engagement pictures (or other portraits) which have a similiar amount of effort. If I have a problem with a portrait I might need to call them back in to reshoot. If theres a problem with the wedding pictures I'm stuck.

The workaround is better preparation, more people, more equipment, etc. All this costs money.

I've shot weddings before. You're partially right, wedding parties are willing to pay, and pay well. The flip side of it is that they can be some of the absolute worst clients possible, and you only have one chance to get it right. So a lot of the "wedding markup", at least in regards to photography, comes down to "how much do I have to get to make the headache and stress worth it?"