Steve Jobs rejected Dropbox and called it a mere feature, not a business, and then Apple created there own version.
Airbnb ... again, it's just a small business at best.
If I could seed my startup idea with $80k I would bankroll the damn thing myself using my own savings, instead of selling my company down the river on a convertible note for a paltry sum. Yes, I have $80k to blow because I have real experience making real money. No, 80k does not come anywhere close to the investment needed to seed a real business.