I didn't know they were that cheap. A new refinery starts at about $5B.

Why the moaning about nuclear power plant cost if refineries sit at a similar cost?

Refineries return that money faster.

Human lifespan is short. So things that affect one human lifespan quickly are scarier. Radiation scares people because it can kill them fast. Effects from oil and gas tend to take much longer.

What kind of things go into a refinery that form that price?

Engineering costs, inspection costs, a lot of stainless steel tanks and tubing, a lot of stainless steel valves/clamps/misc attachments, a lot of stainless steel welding that needs to be certified, redundant failsafes, various safety devices/monitoring systems, etc. I'm sure some bribes are buried/hidden in these costs as well, such as if you allow this oil refinery we'll use your construction company and you can over charge us so any payoff is legal.

MM=B?

In the financial world MM is used to mean million.

M is 1000 in roman numerals. MM is one million.

I think MM is 2000 in Roman numerals, no?

You are technically correct, financial dudes like roman numerals but somewhere in history someone (probably someone reeeeeally powerful) started using MM for million and thus started the trend.

Aside, swiss watches tend to have a watch maker's four on them instead of the more correct IV... and apparently there are a bunch of other variations out there[1]. Though MM is still quite stupid.

1. https://en.wikipedia.org/wiki/Roman_numerals#Variant_forms

I believe the thought behind MM is "a thousand thousand", using the roman numeral as if it were a positional digit.

Not sure how someone got the idea to do that...

Algebraically it makes sense I guess (M.M)