Amibroker is best buy. Amibroker costs around 279 US Dollars.
F charts free version contains only limited tools. But if you buy Fcharts Pro, all upgrades will be free. It is lifetime upgrade licence. Incase of Amibroker I think only next five upgrades are free. As per my memory FCharts Pro costs around 180 Australian Dollars. I am saying it only from my memory. So it is subject to correction.
Hope this helps