empty pockets
I would bear in mind what you want to do with it once you have bought the 'cheapest' ATPL in town. For instance, if the cheapest happens to be an FAA ATP then that is of limited use to you in the UK (which is where I am guessing you are looking at using it from your profile.) If you then have to convert it over here then it could cost you a small fortune, I am not up on the exact costings these days but it has nearly always worked out more expensive than just doing it here in the first place as JAR land give you very few credits for your US time and qualifications. I know you can do JAR courses in the US now, so maybe that will make a difference.
Someone on these hallowed pages will have the details for you, my point is merely to state that the most obvious 'cheapest' may not necessarily be the actual cheapest in the long run......do take everything into account when deciding on the cheapest........
PP