Hi,
I run a number of Instagram pages and have three pages that I personally own with close to 100K followers on each, 500K total. I also have a network of clients with even more pages that have over 100K followers
As for your project, I would be more than happy to promote you on a number of pages and try to get your 15-second challenge viral. Because I'm not 100% clear on what you are after its difficult for me to price this correctly, let's have a conversation and work out exactly what you and then I can either lower or raise the price so it reflects the amount of work.
Best,
Sam