People pay a certain amount of money to have a wall plaque with their name on it, displayed at your premises. Buy-a-brick is another variation on this theme where people pay for their name to be etched into a brick inside (or outside) of your premises.
This works particularly well if you are getting new premises (especially if you are building them). However you can still do it at your existing premises.
What do you charge? Well, basically as much as you can because these are generally permanent displays with only one chance to collect payment. I would suggest that you set the price at a minimum of $50 but $100 is more normal. If the plaques are reasonably small anything between 100 and 500 sales would be quite normal.
As fundraising events go its a great money earner and if you have premises don't leave it off your list.