Retail: you can get a solid grey or charcoal wool suit from H&M for $250 and some lace up shoes (Cole Haan, etc.) from a discount retailer (DSW, Nordstrom Rack, Filene's Basement, etc.) for about $100.
Online: On eBay, you can probably get a nice suit (Ralph Lauren, Brooks Brothers, etc.) for less than $200 and nice shoes (Allen Edmonds, Alden, etc.) for less than $200.
Thrift: You can probably get a suit for less than $20 and shoes for less than $15.