Tipping the reverand at our wedding?

when i was looking for a minister/celebrant for our wedding,we found a company that provides you with a Reverend and the info they gave me said that the total fee came up to 450 about with everything included,but when we met with the Reverend and signed a contract,he bluntly said;most people tip anywhere from 125-250$. i was kind of taken back, i felt it was kind of rude for someone to push a tip on us and especially it being so high.my boyfriend is pretty mad about it and wants to only give him a 20$ tip but im scared we'll come off as rude.i don't know what to think. any suggestions,ideas on this tipping thing?