I routinely get offers of an extra $5, $10 and sometmes $15 bonuses either by email, text or occasionally phone calls. I've negotiated a $25 bonus on a phone call once Figured they were desperate.
Do not read so much, look about you and think of what you see there.
Richard Feynman-- letter to Ashok Arora, 4 January 1967, published in Perfectly Reasonable Deviations from the Beaten Track (2005) p. 230