Fix Shopify Cost Discrepancy

I’m seeing a worrying gap between my ad metrics: every paid link click costs me X, yet driving someone to the landing page ends up costing three times that. Something inside the Shopify storefront is causing visitors to drop before the page fully loads or engages, and I need that fixed quickly... (Budget: $10 - $30 USD, Jobs: Analytics, HTML, JavaScript, Page Speed Optimization, PHP, Shopify, Web Development, Website Optimization)