According to a screenshot taken by the folks at Engadget, it looks to us like the cheapest HTC One on contract will be priced at $250. Engadget did not receive any official information regarding the flagship's pricing or specific availability. But this should give you some idea what the plans of AT&T will likely be.
The 64GB model looks like it will take a bit more time to get out of the gate, though the tipster says it will cost $299.99 when it's ready.
Other than AT&T, T-Mobile has announced that the HTC One is "coming soon" for $99 up-front, and rumors earlier today suggested Sprint's model would cost $199.99 with a two-year contract. AT&T's rumored $249.99 price-point would place the HTC One in direct competition with Samsung's Galaxy S4, which is already the clear winner when it comes to popularity.