I found this out the hard way. A provider I had my eye on in RM started advertising on FB. I saw the price and thought I would take the plunge. I contacted him through RM cause I am a member there. The price he quoted me was $80 dollars higher. I was caught off guard and declined. He asked if it was because of cost and I told him I saw his price on FB. To his credit he offered to meet for the FB price but by then I felt I would be cheating him and felt embarrassed because I felt like I was haggling over price. Lesson learned.