You could switch to a saddle that isn't as abrasive. That's one of the reasons people like leather saddles such as Brookes -- even if they're more expensive and heavier than plastic wonders. The leather saddles also breathe and wick moisture and I've found that wet cloth abrades much faster than dry cloth.
![Brookes leather saddle](
There are also neoprene saddle covers which might reduce friction by allowing more slippage, but I've always found the squishy movement they cause to be more uncomfortable than comfortable. ![Generic saddle cover](
ps. Many cyclists consider saddle worn clothing to be a mark of pride.