If you prove that the cost of getting a new customer means you are not making a profit on what you sell, consider increasing your prices to accommodate this.
Regularly check how much each result is costing you, because it will fluctuate day to day.
If you’re stuck on a couple of hundred followers, consider a paid campaign to get more people to like your page rather than buy your product.
Don’t just rely on the platform’s algorithms to target ‘vegans’ in paid campaigns, look at other ways to ensure you are reaching the right audience.