If possible, you should buy pharma drugs like this from India. Accutane (isotretinoin) is cheaper and more reliable from India compared to UGLs.
I was recently quoted Isotretinoin 20mg at $1.10 for 10 pills. That's 100 pills for $11 ($0.0055/mg) which is cheaper than most of the UGL 10mg pills.
How much do you weight?
If you're 100kg and aiming for the target total of 120-150mg/kg then you need 12,000-15,000mg. That's a grand total of $66 to $83.
Can't ask for much cheaper and now's the right time of year to buy.