$20 + $5 for the import fee so $25 total to get it to the US. The cost of shipping once it's here depends on who you use as your transhipper. Normally it's around $39 for express and $20 for priority. This page will give you a better idea,
Most of the time the bettas pictured are what you get. Sometimes the colors will be a little different do to stress after shipping but they'll color up once they settle in. Also thai breeders sometimes use different terms for colors such as "green". What they call green tends to be more blue so keep that in mind. Colors such as marble may also look different once you get your betta. Fish are shipped every two weeks so what a marble looked like when you placed your bid may look different at arrival to your home. Make sure you check a sellers feedback. Most thai breeders aren't going to have 100% and thats ok but don't go with someone who has poor feedback and always read the comments too.