Jamie here from Shopify. All US Shopify merchants using Shopify Payments with over $20,000 in gross sales and over 200 transactions are required to submit a 1099k form which will be provided by Shopify. This is based on gross sales, not net, and will not factor in refunds. Using your example you would indeed receive a 1099k.
I hope that helps!
This is only based off of orders placed using Shopify Payments, and does not include other payment gateways/methods. Each store is unique to Shopify Payments, and we do not lump together users/businesses that have multiple stores into one account at this time.