With heatsink, casing, shipping (from USA?), it easily go way beyond 550USD.
Bro, just go and contact Razali (Dr Evil - DELighting) and enquire MaxSpect. Ask him to quote you with CREE LEDs.
You will have a nice fixture, proper casing, proper mount, 18 months warranty, built in timer, built in high temp protection, moonlight. You will also eliminate the hassel of looking for heatsink and DIYing ugly housing.
Need I say more?