I'm not sure whats causing the confusion or concern. It's 100% a mertensii. And the color could be accurate, though the tips are probably not as bright of an orange as they appear in the photo. Mertensii typically have bright red verrucae that become red lines towards the foot, creating a bright red base. They're actually almost the opposite of gigs, where the verrucae fade towards the foot. It's unfortunate that the foot is typically the most colorful part of a mert, where the oral disk and tentacles are oftentimes drab brown or green. In terms of size, it looks like it's acclimating which mean it could feasibly double or even triple in size.
I've seen three merts in person, and all except one looked like the one in the photo. All three were extremely small -- less than 6" across. The one that didn't look like the photo was badly bleached and got chewed up in a powerhead. My friend gave it to me and I tried to bring it back from the dead, but the powerhead chewed it up all the way to its mouth, and since it was bleached, it couldn't get any nutrients (no zooxanthellae and a ripped mouth so I couldn't feed it), and it eventually starved to death. However, the entire time, it had bright red verrucae.
Regarding price, given its rarity, a dollar amount is hard to determine. My friend picked up the one I tried to rehabilitate for $40 because the LFS didn't know what it was. The other two were at another LFS, and because they knew what it was, they priced it high and waited for a buyer of rare anemones. Both times we were able to place the nems in capable hands -- actually members of RC -- for what they were asking (though it was less than $500). When you think about the price of red haddoni, especially when sold via Live Aquaria, $500 for a mertensii doesn't surprise me.
. I'll post a little later. Cheers.
