Well, I think it’s unusual to bill per hour for the cooks. The only time I’ve seen cooks billed per hour is when there are stations (omelet, pasta, carving, etc.). Otherwise, that’s usually built into the price of the food, so I probably would have expected to see a higher price tag on surf and turf than $30 to build in labor costs on that.
As for the rest, it’s really variable by what kind of buffet you’re having. A very basic informal buffet where people are serving themselves from a single line of food would require two servers for the first 25 people and then an additional server per 20-25 people thereabouts. If people are being served off the line, then you’ll need more servers. If you’re having stations (carving, pasta, etc.) then you’d likely need a cook and a dedicated server for each station. If you aren’t having stations with active cooking, but are dividing up your buffet line into stations (i.e. the salad line is off to the left, entrees and sides to the right, etc.) you’ll need a dedicated server for each regardless of whether people are serving themselves. If servers are going to be refilling water, coffee, or wine carafes at the table, setting out salads tableside or refilling bread baskets, you’re looking at one server for about every 10-12 people instead of 20-25, and usually a waitstaff captain when you have 5 or more servers.
That said, depending on location and formality, I don’t think $93/pp is necessarily extreme. It would be for many places where I live in the Midwest, but would be downright cheap at more formal places here and on the east coast. It’s just that normally all of this is rolled into a single cost (or single cost plus percentage service fee) and you don’t see the breakdown.
I will say, depending on the formality of your dinner, I would caution against going less than 1 server per 20-25 people for a buffet. I’ve seen the disasterous results of when people try to get by with less thinking “It’s a buffet, people are serving themselves!” It usually results in hungry people standing a long time in line for things to get replenished and people getting frustrated when dishes and glasses are piling up and crowding the table because the servers can’t clear them fast enough.
So at a minimum for the most basic of buffets, precooked and arriving in a hotbox, no table service except for clearing plates, I would expect no less than 7 servers and one captain plus a catering manager and three bartenders if liquor is served, two if only beer and wine. Then depending on whether any cooking was happening onsite, set-up and level of service I would go up from there. So I would ask for specifics on who is doing what and the level of service that provides and negotiate from there.