Well, I happen to know this for a fact, since my wife is a FTD who just completed her Advanced standing program. Bench tests are for all practical purposes non-existent. Maybe one or two states have them.
Yes so you can try this path, in these states (I think Minnesota is one) if saving money is your primary goal. After you get your license and work for a couple of years you can get license by credentials in most states. So that's not a terrible option.
An FTD can expect to pay 50,000 - 90,000 PER YEAR for 2 -3 years to complete their advanced standing program. 5 years for Indian BDS + 1-2 years sitting out studying for NBDE and getting ADV. standing admission and paying for living expenses in the US + 2-3 years Adv. Standing Program to get the DDS in order to finally get licensed = 9 - 11 years STUPID LONGER, and MORE EXPENSIVE OPTION than 4 years US college + 4 years US dental school.
first $50,000-90,000 compared to what? I'll tell you, compared to $50,000-90,000 in many schools, since most private schools charge about the same for the adv. standing program and their regular DDS (examples are USC, UOP, tufts and many others), so unless you can guarantee you'll get into a regular DDS program in PUBLIC school then, there is no difference during the 2 years. Needless to say, public schools are more competitive, specially the decent ones.
Second, the overwhelming majority of programs are 2 years only (eg. UCLA, UCSF, UOP, USC, Loma Linda, BU, tufts and many others). It's important to clarify that.
Third your proposed time line is something I have never seen done before, being a FTD myself who have just finished my adv. standing program. No one takes 2 years to study for part I and no one would spend these 2 years in the US unless burning dollars is a hobby of his. In reality most people study for a couple of months in their country and even apply from their ( you only need to be here to take the test itself and attend interviews).
Besides what about living expenses during the 8 years if you were to take the other option.
Having said that, there are some benefits to completing all of your education in the US. Specializing might be easy if you're interested, also you have a wider selection of dental schools to get into.