Established companies will use their massive advertising budget to shit all over your product and get exclusivity contracts which make it very difficult for you

Established companies will use their massive advertising budget to shit all over your product and get exclusivity contracts which make it very difficult for you to spread because you spent your money on engineering. Your repeat customers will be decades away and surviving decades until that point is difficult. You could offer good repair and part replacement services to help but that has a lot of overhead and organizational costs itself.