It was around $10-11 per 100g for the mud crab at Jumbo's East Coast, considered more touristy and more expensive than other places.

We also went to Chicken Pie Kitchen and tried the Black Pepper Crab Bee Hoon (among other things) - it felt like the price was similar...

That works out to be around $70 USD for a 2lb crab. It's not cheap, but it's cheaper than getting crab at a nice restaurant in Seattle...