The fee you're going to pay will depend on how congested the Bitcoin blockchain is. It's not fixed at $3. It could be a lot higher if there's a resurgence in network activity. Altcoins (although many are centralized) are a much cheaper option than the LN (when taking into consideration paying a one-time fee on the BTC blockchain). Besides, the L2 network isn't ready for mainstream use. It's full of bugs. If the LN experiences an outage or collapses, you can say "bye-bye" to your sats for good.
Things aside, I think it's possible Bitcoin will reach Gold's market cap. Especially when a lot of prominent institutional investment firms are showing huge interest in it. I'd say we are still early to the game. Once BTC "explodes", market prices will be a lot higher than what they are right now. Perhaps, it will replace Gold in the future?