My recent purchase from Paris concluded that it will be cheaper than US. Also Paris has a lot better inventory so you will be able to get what you want with no waiting and that's priceless.
My 35 PWH swift birkin in BDP was 5700 Euro
Transaction could've been done two ways
5700 Euro x Spot rate and x 2% - 3% card fee from your card company for foreign currency transaction
or 5700 Euro x 1.52 exchange rate (FSH automatically charge you in USD after exchanged to VISA or Mastercard only but you save on the currency fee)
Tax return is about 12-15%? so i'll probably get at least 10+% back after fees or what not.
That means it is about 5130E Euro after detax which makes it around USD7800 with current rate and fees. From the pricing thread it seems like a comparable birkin is over 8200 pre tax? so it is def cheaper in Europe
and i can not stress enough on the availability of color/leather and the overall experience etc etc.
H France tax refund is 10% flat. Yes, they do the processing themselves and they want to make some $$$ on it too (at least that's my take on it)!

In conclusion, with sales tax in US (typically +7-9%), it is almost always cheaper to buy in EU countries, particularly if you take into consideration of the tax rebate (-10%).