There are several ways to approach this question, but one is to look at
completed sales on eBay---when I do that (and limit it to US sales only?--I gather you're also here in the states) I
get the sense that SWE's price is on the high side. I'm seeing $2,400 to $2,800 as the more typical range. There are, though, a lot of variables: condition, service history, whether it's a "complete set" (if that matters---I'm of the mind that it doesn't, for older references like this, but many will disagree), etc. And buying from a large dealer like SWE comes with other advantages that might be worth a few hundred extra. You can pay with credit card (which offers some amount of protection), you know you're going to get your watch---no funny business, as can happen with a rando on the internet---they will make sure the watch is keeping good time and will pressure test it, and it comes with their in-house warranty and a return policy (just read the fine-print on that--I think the return option is voided once you remove the stickers). I still think $3,150 is a
bit high, but if it's a full set, in great condition, and if this added peace of mind is worth a premium to you, then it's not wildly out of line, I'd say.
I'm not finding the listing myself---are you sure it's not an already-sold piece? They don't remove sold listings on their site---which I actually like, from a research standpoint. I'm seeing
two of them for $2,990. Even better. In the fine print, you'll see that one will fit a 7.5" wrist and has the (long expired) Omega warranty card, and the other will fit an 8" wrist but has no card. Neither has a box. Tough call, but if I were choosing, I'd get the one that presumably comes with an extra bracelet link or two, rather than the useless piece of warranty card plastic. I'd say hang on to the extra links---if you ever go to sell the watch, they'll be good to have. But if you choose to sell them instead, they can be worth $50-100 apiece, depending on condition, so if you're selling several of them to get it down to your wrist size, you'll recoup considerable money.
I've
only had good experiences with SWE, and I know most others have too. But in the interest of full disclosure, you should be aware of
this now-infamous story, as explained on the Rolex Forum. The issue was resolved, as I understand it, but it remains a blemish in their history that anyone buying from them should know about.