React Native - Native module vs JS performance - react-native

Question

We have need for faster price calculations in our app. Currently we iterate over product items in JS and calculate each product item’s price. I was thinking maybe native modules could be used for faster speeds. But it doesn’t seem like it?
When I test a simple C++ native module with performance.now() its slower than the JS equivalent. Its just a for loop of 20 iterations of a multiplication.
I guess there is some kind of overhead (JSON parsing?) when using native modules.
First I tried using the promise based RCT_EXPORT_METHOD way and the first execution would take about 15ms.
Then I tried RCT_EXPORT_BLOCKING_SYNCHRONOUS_METHOD but it was still slower than JS. It took about 0.4ms first execution.
JS would take about 0.0025ms first execution.
Is native modules for just iterating and calculating prices a bad idea/will it not be faster than JS?
The code:
int multiply(float a, float b)
{
for (int i = 0; i < 100; i++)
{
int test = a * b;
}
return a * b;
}
// Native module
React.useEffect(() => {
const p1 = performance.now();
const test = multiply(3, 7);
const p2 = performance.now();
const result = p2 - p1;
console.log(`A: ${result}`, test);
}, []);
// JS
React.useEffect(() => {
const p1 = performance.now();
const test = 3 * 7;
for (let i = 0; i < 20; i++) {
const a = 3 * 7;
}
const p2 = performance.now();
const result = p2 - p1;
console.log(`B: ${result}`, test);
}, []);