ME trilogy DLC situation is a bloody mess on PC due to how they originally setup the system to use bioware points. You'll have to wait for the rare sale on the points, otherwise it'll just never be a good price.
The Trilogy edition is just a Blood Pack of shit for not including DLC.
For Mass Effect 2 and 3 there are finally all DLCs as a bundle in the regular store to buy. With $25 or $30 there are no special offers but its still cheaper than before.