Bulk selling without TFT

Seriously, how do you do it? I've always been a big fan of delirium farming, and scarabs are money. I can get about 70 divines of scarabs from 38 divines worth of maps, but selling on TFT @ 85% ninja price, I'm getting just 60 divines. I understand that time is money and that I'm paying for convenience, but I'm leaving quite a bit of money on the table, especially since the ninja price doesn't take into account bulk pricing.

This isn't just about scarabs though - In general, how do you efficiently bulk sell straight to the trade website?