The $277 version on Amazon is the recently discontinued (I think) 374, the current model that goes for $500 ($400 at TEquipment with EEVBlog discount) is the 374FC which has "Fluke Connect". I doubt the Amazon one is grey market, you can probably buy it and register it with Fluke--and if they won't register it, you can send it back under Amazon's return policy.
Edit: I just looked and the seller is Japanese, so it actually might be grey market as this model is still available outside the US. But not counterfeit.
Yep, the 274 US seems to be the non-BT version 374
https://www.amazon.com/Fluke-True-RMS-Clamp-Meter-600A/dp/B004E248XA374FC is 410US
https://www.amazon.com/FLUKE-374-600A-Trms-Wireless-Clamp/dp/B017OVC2GW/Both of these Amazon US offerings seem to be operated by the same Chinese store. [YuByKa] will give a clue about the price jump between Fluke374 versus the Fluke Connect able BT version, when it's the same seller.
CN seller
https://www.amazon.com/sp?ie=UTF8&seller=A30SFQDM752KB9&asin=B004E248XA&ref_=dp_merchant_link[Business Name: Shanghai Yubyka Information Technology Co., Ltd]
Though still attractive US prices, here in northern Europe [Denmark] lowest pricerunner is 725 USD (Fluke374FC 4900 DKK)
https://www.pricerunner.dk/pl/345-3308293/Elvaerktoej/Fluke-374-FC-So people here in Denmark would definitely purchase from the grey overseas market USA Amazon..

- as the 410US Fluke 374FC on US Amazon lists the DK VAT-import & shipping as a total of another +129US (539US total / 410+129) while the older 374 non-FC seems to be outsourced here.
Uhmm' for those lucrative attractive overseas grey-marketprices where you can save 25% to 30%, but it's Denmark in a nutshell, sadly.. prices here are ludicrously high, Eurostat just came with their annual consumer report, showing Denmark as a superb nr1 on consumer-prices (it's a negative stat) and +50% above the EU average. sure the income & salaries are very high here, and generally high living standards, but the problem is that many people will purchase from abroad, often other EU countries or the USA or the Far East and that kills the home market, when it's so difficult to compete on prices versus other regions that operate with very different living & income standards.