Kinda depends. Superspeeds are plentiful, so they usually don't garner that much cash. If it's a flare-tip model from the 50s and it is used but in really good shape, people will probably be willing to pay between 13 and 17 bucks, maybe a little more if it's really pristine.
But that has reallly no bearing on "fair market value". Hey, I got a decent condition undated Super Speed for FREE on eBay (Seller incorrectly packed an Old Spice mug bought with it, and it was nothing but shards when I opened it, causing a slight puncture to my finger- Seller asked that I keep the razor plus accept refund for my troubles- I gladly obliged).I picked up three 40's era super speeds in remarkable condition for about $12 total.
$15-$17 including shipping should get her sold.
But that has reallly no bearing on "fair market value". Hey, I got a decent condition undated Super Speed for FREE on eBay (Seller incorrectly packed an Old Spice mug bought with it, and it was nothing but shards when I opened it, causing a slight puncture to my finger- Seller asked that I keep the razor plus accept refund for my troubles- I gladly obliged).