Brand new they run about $500. With the Tavor 1.5 version there were a few deals going around as people dumped the M21. Most went T1 or Eotech if not going for magnified optics. This left a few out there for around $300 with the QR and bullseye reticle. Those dried up quick though with the flood of 2.0 full rail Tavor rifles.
You should be aware that the main shortcoming is washout from dark to bright. Also size compared to a T1 or RSA. But they do work well with firearms that have the charging handle on the left. Plus with QR and bullseye reticle they were a bargain for a while. I just added the WOR to both my M21 sights. This fixes the washout issue.
You can still get them new. Zahal? I recall a sponsor had them.
Here you go. Wolverine is selling a demo $475 QR and bullseye reticle. Unless you find one on the EE, that's the best price you will find from a retailer. Be careful if buying to insure the mount type. There is original 1.0 Tavor mount which is proprietry, pic base and QR. You want quick release.
On a side note the QR with bullseye reticle along with factory pic rail was a $300 upgrade on the 1.5 Tavor.