Not necessarily. A used SVTF header can be had as low as $100. My dad bought a Focus oilpan on ebay for $50, and I've seen them at starting prices of $15. The expensive part is gonna be to hook up the header to the exhaust. That's gonna have to be a custom job and if you can't weld or get a welder to do it cheap, it will run you an easy $100. But if you can get it done for around $250 total, that's as cheap or cheaper as a new header. But yeah, it won't be easy and a 4-1 header will only give you around 3-5hp and tq more than the SVT header.

2000 Rio Red I4 Cougar 200whp & 210wtq at 9psi 254whp & 276wtq with NX 35shot WRX TD04 Turbo, Cut Short Shifter, Strut Tower Bar, 17" ZN Wheels, Roush Springs, Starion Intercooler, NX 35 shot, HKS SS BOV, Full 3" exhaust,StreetFlight Chip