There are plenty of good saddle for sale advertised as new by "experienced" sellers with good reputation at very low prices... 60-70%

Any way of making sure these are genuine saddles?

Not until you have it in hand.

Also sometimes you can just look at every little detail and see if something is off, if its fake. That includes all markings on the bottom of the saddle and the rails, materials even sometimes...Though some might pass that test.

You can look at the feedback left for the seller to see if anyone has said anything about the saddles. You can probably check to see if they are authorized to sell the product by calling the company. And buy from those who offer easy returns, JIC.

If a saddle has a list price of $250 and a international seller has a new product for $29.99. It might be a knock off.

Remember the old adage "Anything to good to be true, is probably not true".

Caveat Emptor - Buyer be where.

Buyer be in California according to his profile...

Buy with paypal. if its fake, submit an issue and get your money back.

There's a website openly selling Fizik knockoffs for around $20 or so. Says right on the website the saddles are "replicas" or something like that. Feedback indicates they will refund for customers who didn't notice the explanation that the saddles weren't real Fiziks.

Pretty safe bet that there are dozens of less scrupulous sellers on ebay selling "replicas" of expensive saddles without informing buyers.

And FWIW you can buy genuine discontinued Fiziks for around $50, although most are oriented toward mountain biking.

Look around at the normal web stores. Some brands will sell for 25% below MSRP all-day long on a dozen different sites, finding a few saddles that are 40% off isn't that un-reasonable, because no one sells them at MSRP.

Other brands are like Specialized, and sell only at MSRP, so you won't really find a new saddle for more than 20% off.

Beyond that you can find tons of "new/used" saddles on ebay. Basically, these are people who bought a saddle to try and didn't like it, but couldn't return it. They are properly considered used, but may be sold as "like new" with original packaging.

Where should the buyer be?