The terms "good supplier" and "cheap" are rarely found in the same sentence. Meaning you usually get what you pay for.
Also, I think nealtw's numbers might be a bit misleading. For 100 S.F. at 1-1/2" thick (0.125'), the volume computes to 12.5 C.F. Normal flagstone, having a density of 95 Lb. per C.F., will weigh about 1188 Lb., rounded. Quite a bit shy of the 1 ton yield you asked about.
Conversely, 1 ton at the above density should result in material about 0.21' thick, or about 2-1/2".