How do I reach the level my friend / supplier did when he was on Amazon?

I sell low ticket DIY fashion items on Amazon. I do between 6-8k / month in sales on Amazon.

But back in 2018 before my friend who is my supplier stopped using Amazon he was selling the same items and clearing 40k plus a month.

In utilize CPC he didn’t. I’m set up very competitively when it comes to pricing.

I’ve been selling on there for 3 years now this month.

Any tips of advice to scale much appreciated, CPC is difficult to increase for items of such low cost.

Thank you