You have to take a punt on what styles/sizes will be popular and end up flogging old stuff at trade just to get rid.
If you give someone 10% off that 1/3 of your margin gone. That’s margin, not profit.
You’d be surprised the amount of time it takes to keep a clothing section organised. We had one bloke pretty much just sorting clothing, hanging up, pricing, ordering etc. for half his time in the shop.
It can get tricky when anyone can come in, try it on, then buy it online for pretty much the same price that we could get it for. You can usually spot the internet-buyer though, they just seem shifty/guilty. Especially true for shoes.
Price wise, everything is different, sometimes we could get stuff at 40% margin, others 20%, I guess it all balances out though.