The PID controller is definately worth it.
And really, if you're DIYing, isn't that expensive.
My breakdown was this:
PID controller was $13, power switches and socket go for $4, thermocouple is $4, $2 for the plastic Dollarama bucket, $10 (5 each) for DC pumps, $3.50 power cord, $7 heater, $14 for GFCI recepticle. Plus some wire, solder (not necessarily needed), morettes (again, not needed), electrical tape, etc. Everything but the GFCI, wires, electrical tape, etc. were ordered off of eBay with free shipping.
I also purchased relays, but ended up killing one and went without as the PID controller already has.