Not on Amazon, but on Charm - my favorite wonderful aquarium supply and live fish site.
They have sales every day updated at 6pm, so I browse and browse... then add everything up and see I could never afford it. But I can dream.
Their standard "Betta Kit" is a $100 3.5g tank with soil, filter, heater, and light. Their "mini" kit is a 1.2g, and includes a filter and heater.