Magento 2 : How to fetch custom input data in product attribute form

First of all you need to create a data patch to create field in eav_attribute table. It will save data in db and fetch data in product attribute form

<?php

namespace Vendor\Module\Setup\Patch\Data;

use Magento\Catalog\Model\Product;
use Magento\Eav\Model\Entity\Attribute\ScopedAttributeInterface;
use Magento\Eav\Setup\EavSetup;
use Magento\Eav\Setup\EavSetupFactory;
use Magento\Framework\Setup\ModuleDataSetupInterface;
use Magento\Framework\Setup\Patch\DataPatchInterface;

class Data implements DataPatchInterface
{
    /**
     * @var ModuleDataSetupInterface
     */
    private $moduleDataSetup;

    /**
     * @var EavSetupFactory
     */
    private $eavSetupFactory;

    public function __construct(
        ModuleDataSetupInterface $moduleDataSetup,
        EavSetupFactory $categorySetup
    ) {
        $this->moduleDataSetup = $moduleDataSetup;
        $this->eavSetupFactory = $eavSetupFactory;
    }

    public function apply()
    {
        $eavSetup = $this->eavSetupFactory->create(['setup' => $this->moduleDataSetup]);
        $eavSetup->addAttribute(
            Product::ENTITY,
            'stn_price',
            [
                'type' => 'text',
                'label' => 'Stone Price',
                'required' => false,
                'visible' => 1,
                'visible_on_front' => 1,
                'global' => ScopedAttributeInterface::SCOPE_STORE,
            ]
        );
    }

    public static function getDependencies()
    {
        return [];
    }

    public function getAliases()
    {
        return [];
    }
}

After creating this file

Run commands:

php bin/magento setup:upgrade and others as required