If you find a 1972 Kenner Blythe doll out of box and in good condition you could be looking at $800 - 1200 US. Like I said before, it all depends on the condition.
Even the Japanese reproduction Takara blythe dolls can fetch anywhere between $100 ~ 2000 US. Sold out dolls, BL Takaras and Limited edition CWC Takara Blyte dolls usually go for the most.
Typically out of box, damaged, used and nude dolls go for the least so if you are on a budget that may be a good start for you.
A great tip is to check completed Ebay auctions to give you an idea of what something is currently worth. I actually do that for anything that I am going to sell just to give me an idea what to start the price at. You do this by hitting the advanced search tab which is right beside the normal search tab and then select the completed auctions tab.
1972 Kenner Blythe doll - The original Blythe doll made by the Kenner General Mills Fun Group for only one year. These dolls are worth anywhere from $650 - 5000 US depending on it's condition.
1972 Kenner Blythe Doll
BL Blythe (bogged eye with a licca body) Takara CWC Hasbro started producing these reproduction Blythe dolls in 2001 and they are currently worth a pretty penny. Anywhere from $200 - 2000 US - Parco was the first doll BL-00 and she is worth thousands because there were only 1000 pieces issued.
BL Parco BL-00
BL Mondrian BL-01
Next are the EBL, SBL and RBL Takaras and those range from $100 - $750 US. If they are limited or rare then you will see them worth more.
EBL - Excellent Face Mold
SBL - Superior Face Mold
RBL - Radiant Face Mold
ADG are the Ashton Drake Blythe dolls and they are worth $70 - 250 US. The Medieval Mood doll is limited at 1000 pieces so she is worth more.
ADG - Medieval Blythe limited to 1000 pieces, I believe.
Love, A xo