Also, they've said they can provide a taxi transfer (one way) for 90 US dollars. I take it this is a bit steep?
A little bit, although prices in Moscow going through the roof arguably it is worth it for some piece of mind. If you opt for getting a taxi at the airport,
don't take the first price on offer. Force your way past the scrum of drivers and head towards one of the taxi kiosks. The closer you get the keener the price becomes.