Math done! The oven draws less than 1 kWh during the process. Despite electricity being rather expensive over here in The Netherlands, it still costs me less than half a Euro.
Apart from this, I think a low-cost sets show inconsistencies. I'm using 10 Euro Warwick sets on my cheap P-Bass. Sometimes one of the strings is dead, straight from the package. Sometimes intonation is poor, due to inconsistencies over the length of the string.
The tone before and after treatment, is a matter of taste and/or requirement.