Break chance is 4% and repair cost is 5%. That means every 25 ticks you break everything, which costs five percent of your equipment value.
In 25 ticks you make 1250 gold. multiply that by 20 to get value of armor and you get 25,000 gold.
So 25,000 gold per multiplier is the amount to sustain your equipment. You will have to decide what your average multiplier is. It is probably around x2. So about 50,000 will break even.