Lots of noobs in here who didn't take statistics.
Assume a 4% chance of item break every minute. Assume gear is 6 different items whose average cost is 5000 gold, totaling 30000. Every repair on average is therefore 0.07*5000=350 gold.
There are seven discrete outcomes for an average minute of gameplay...between 0 and 6 items will break. Let us calculate these probabilities.
No repairs = 0.96^6 = 78.28% chance to pay 0 gold
One item broken = ((0.96^5)*0.04 * 6 combinations = 19.57% chance to pay 350 gold
Two items broken = (0.96^4)*(0.04^2) * 15 combinations = 2.04% chance to pay 700 gold
Three or more items broken = 0.11% chance (fuck outliers). I'm lazy so lets just say 0.11% chance to pay ~1400 gold
Now we weight the costs with their probabilities...
0.1957 * 350 + 0.0204 * 700 + 0.0011 * 1400 =
an average of 84.315 gold spent per minute on a 30000 gold equipment setup.This necessitates an average multiplier of between 1x (50 gold per minute) and 2x (100 gold per minute) to break even -- not terribly hard.
Repair costs exist for a reason - as the game's main gold sink. Gold is useless without repair costs.