Let's do the math. We already know that repair cost is 20% of the original, so 1/5. If you have 20k worth of gear, then if everything breaks (which is very unlikely), you lose 4k.
I gain 50 per minute, rounds are 7 minutes each. That means 350 gold for every x1 round. I know these numbers don't differ much from yours, but the final result is far less: that means 12 rounds to finance a full repair, not 20. Those were the numbers I know for sure.
Now, other things:
- Your whole set doesn't break in 12 rounds, you have to be extremely unlucky for that, especially considering that:
- No matter how unlucky you are, you won't lose all your rounds
- Expensive items seem to have more 'durability' - they break less often, so mostly you have to pay for the cheaper parts of your gear
- It's very unlikely to stay at multiplier x1 forever. A winning streak of four, and you've got your upkeep problem mostly covered - and that's not something impossible.