I believe there's an online spreadsheet somewhere with the overall cost of going to Suporn and Chettawut. In Thailand Suporn's the most expensive and longest wait list (not sure but I think its 595K baht and 18 months, plus hotel). I think Dr Chettawutt is 2/3 that and a few months wait list. There's been some positive posts recently here about PAI as well.
You only need one letter for Suporn, he provides the other. Dr Chettawut wants two, but will provide both if you pay extra.
I've heard the online psych Dr Graham Peveller will provide a suitable letter.