These are just my experiences, you can take it with a grain of salt
Others may chime in:
Your car and the petrol to fill it will be much higher in Singapore. Also the cost to park it around town, some days I go through another S$20. for parking and ERP charges.
The price for comparable housing will be much higher. If you wanted to rent a 4 bedrooms, 2 1/2 bath house in Singapore -- it would cost USD $20K/month, however a tidy little condo
could be found for $3K- $6K, fairly close to town with amenities.
Any imported food is much higher in cost than in the US. Even for an item imported to the US from Australia vs. the same item imported to Singapore. Think double.
Liquor and tobacco prices are double, or more.
Books and magazines are 25 - 50% higher (so there are lots of good used books stores around).
If you have kids: International School
and their private bus contractors will seriously dent your savings compared to free public US schools.
Depending on your size and taste, clothes and shoes are much more expensive in Singapore. If you want a Polo shirt you have to go to the mall and pay full retail (plus about an additional 20% mark up) at Ralph Lauren, there are no 'outlets' really. If you want a lovely cheongsam made, well -- that will be cheaper. Nine West shoes are at least double.
Live concerts are at least double. When the Poilce came to Singapore a few months ago, the retail for the best tickets (not the scalped price) was around USD$400.
Things that are cheaper in Singapore:
'Local' food, really more like 'regional' food -- Singapore fast food, sold at hawker stands provides a complete meal for under USD $5.
Healthcare (for pets too).
Anything that utilizes manual labour (domestic help, gardeners, tailors, plumbers, electricians, etc...)