It was all profitable. Ad agencies are borderline scammers - they measure traffic and clicks as performance, which makes you to spend more money to increase "performance" and pay more agency fees.
Sometimes I burned $15000 before first conversion, but ROI was always positive in the end.
People launching ads without any experience, redirecting people to homepage and loosing money are the same kind of people trying trade stock market and loosing money, creating their own amateur e-commerce shop and loosing money getting zero customers, hiring high-school nephew for company website etc etc. You need experience, and before that - knowledge.
First, manage your ads in-house. Agencies have no reason to work for your conversions, that's not their business model. Second, don't treat ads like "we'll slap users with our ad and see what happens". Prepare user flow, conversion funnel, dedicated landing pages, drip campaigns, remarketing etc.
Adwords and Facebook are fully-fledged promotion channels and they have to be treated as such. It's a craft which consultants make huge money from - because they know how to bring profits.