There are two different ways companies give RSUs.

1. You get $X of stock grant when you join. This gets converted to number of stocks based on the value of the stock when you join and then the stock vests over the next 4 years. So if you get a stock grant of $400k when you join and the price of the stock at joining is $1000, you get 400 stocks that vest over the 4 years.

2. You get $X of stock grant when you join. This grant gets divided into $X/4 over the next 4 years. The number of stocks then gets decided each of those 4 years based on the value at the start of that year. So let's say you get a stock grant of $400k. So you get stock worth $100k every year. If the stock is at $1000 for the first year you get 100 stocks for the first year. If the stock goes up to $2000 at the start of second year, you get only 100 stocks. If it goes down to $500 for the third year, you get 200 stocks. So upside is capped. You will only get stocks worth $100k each year.

2. is what followed by Coinbase and Stripe. Some other companies are moving that direction as well. 1. is followed by FAAMG.

#2 is just rotten, especially if the grant expires.

They are expressed in dollars, but converted to stocks at the grant-time value, and vested in number of stocks.

Coinbase is different. The conversion to stocks doesn't happen at grant-time value for all of the grant. The conversion happens at the start of every year of the grant life. So if the stock goes up in the first year, you get fewer stocks for the second year (equaling to grant/4 in value). See my other sibling comment in this thread.

It’s unclear to me why this is being downvoted: that is exactly how it works at my (FAANG) employer.