You have to add a proper box and packaging + a printed brochure/manual + shipping (or driving to a local shop to deliver and collect) + due taxes + some extras.
No way an unknown can compete that way , specially in price, with established brands.
2 ways to beat that:
1) have the amp fully made in China for an OEM price of, say, $250 tops
2) establish yourself as a Guru , get some Guitar God to use it , specially to record a big hit or it to be very visible in the background when the equivalent du jour "Guitar Player type magazine) interviews such wonder guy.
Then you can charge U$2600 for it.
Surefire to waste time and money:
spend $1200 to $1800 by building the same old tired circuits but with "first class components": expensive caps, MM iron, Bourns $20 pots, hand turned brass knobs, exotic wood cabinets, real crocodile skin Tolexing, etc.