It's not $300/person. The base price is $125/person. There are food add-ons that cost more and drinks are extra as well (you can order a wine flight for $60/person or other wines/drinks, at your discretion). There is, of course, a tip on top of that as well. So, if you do lots of add-ons, drinks and a big tip, it can get to $300/person, but it can also be done for much less.
There are also special chef's table and other more intimate dining packages that cost more, but again, the base cost for V&A's is less.