50lbs pork your cost about $75 to yield 25lbs cooked meat at say $10 lb $250 minus the $75 for the pork he paid means you charge him $175
Now that is on the low end. Figuring you pretty much on site served it I would be at about $8 per person (but I run a business) 25lbs will be what I cook for 75 people. So that is 75 people X $8 = $600 that would include buns and sauce so if you deduct that and the $75 he paid for meats it puts you around $475-$500.
Long story short no you did not charge him too much but if he thinks so and you are not in it for the money just tell him it was free and remember it the next time he wants something.