I applied for and received a Quota Visa 11 years ago when my work visa expired. At that time, unfortunately, corruption was in play and to be assured of being in the queue for one of the 50 annual US quota visas, I had to pay php250,000 each for both myself and my ex-wife. I understand the process has been significantly cleaned up now and there is a fixed (acceptable) amount now. Probably documented on the Philippines government web site. At that time you had to be in the queue in December for the January issue.
Note: I was told back then that Chinese had to pay 2-4 times what I paid due to the supply/demand.