Yes, Booming Blade can still apply
TLDR; The Thunder Gauntlets can be assumed to be worth well above the 1sp requirement for Booming Blade.
With the official release of the Artificer class and errata on Booming Blade the only key change is the price component requirement for Booming Blade:
Components: S, M (a melee weapon worth at least 1 sp)
Thunder Gauntlets reads:
Thunder Gauntlets. Each of the armor’s gauntlets counts as a simple melee weapon while you aren’t holding anything in it, and it deals 1d8 thunder damage on a hit. A creature hit by the gauntlet has disadvantage on attack rolls against targets other than you until the start of your next turn, as the armor magically emits a distracting pulse when the creature attacks someone else.
So clearly it meets the "melee weapon" part of the requirement but what about "worth at least 1 sp"? There doesn't appear to be any official statement as to the value of these weapons but we can make some comparisons. We're looking at a one handed weapon dealing 1d8 damage and giving disadvantage on other attacks.
Weapons that deal 1d8:
- Battleaxe - 10gp
- Flail - 10gp
- Longsword - 15gp
- Morningstar - 15gp
- Rapier - 25gp
- War pick - 5gp
- War Hammer - 15gp
In terms of what it may be "worth" - a weapon dealing 1d8 of damage, using the above as a comparison, must be worth at least 5gp using the official pricing. The addition of granting disadvantage can only increase that value. The Thunder Gauntlets can be assumed to be worth well above the 1sp requirement for Booming Blade.
For reference here are some examples of items worth 1sp (if the gauntlets were valued at the same level as these items it would still qualify for booming blade):
Club, dice, oil flask, parchment(one sheet), sling.