Set aside a marketing budget, and then basically sell the $10 item at $9, justifying that the $1 difference is marketing.
Have a marketplace. Buy $100 of goods from users selling stuff. The $100 is a marketing expense. Add $100 to GMV.
Have 5k users on Android, 3k on iPhone, 8k on web. Add them up to show the product has 16k users.
Raise money from an angel who owns a conglomerate. The angel forces all his businesses and people working in these businesses to adopt the app that others wouldn't otherwise trust. Use these totally legitimate clients to create glowing testimonials.
As an early stage investor, instead of putting a lump sum into the account, create a dummy company (or several) for the purpose of feeding cash into the startup. When you're raising money, just sign off half a million dollars of consulting fees to show that the startup is making money.
Create a review site targeting the users. Write a glowing review about how amazing this app is. Share it to gullible Facebook groups.