Why do 5 guys and shakeshack cost so much in Singapore? Are they more profitable in Singapore than in the US?

They are not the general fast food that we have generally grown up with in Singapore. They do claim that their meat are premium and could even be using higher end ingredients. Perhaps it is not cheap for them to import these to Singapore and hence, they will need to charge a higher price. They could also be charging a premium due to their 'branding' and being limited in Singapore as well.

At the end of the day, they might not even be profitable in Singapore due to the high cost involved.

Probably because the ingredients to make the burger might be shipped from overseas which can be quite expensive, so this is passed on to the consumers.