Compound itself is not that expensive. US prices are crazy as usual. In other countries it’s $300 for the month. In US you can buy off-brand semiglutide online for $300-$400 for the month as well.
The generics have the exact same active compounds and are regulated exactly the same.
I do not think Amazon or any other non-Pharmacy can legally fill prescriptions for medicines here, brand or generic.
To save money realistic options in US: if paying with insurance Novo Novordisk has some rebate system. And if paying out of pocket - buy in Canada.