The driver was right around $200.00, the amp from ebay I paid $250.00 for. The sonotube and MDF, interior foam, outer covering less than $100.00. You don't have to get an EP2500, an EP1500 will work very well also. I bought one of them for $180.00!
I just finished building an AE 15 with an Oaudio 500 watt plate amp and a regular box for less than $500.00. The guy I built it with has an SVS ultra plus and he said the new sub is better than the SVS. Nothing like a 15 inch driver.
Chuck