Advice Needed

I just sent my Canon SL1 to a major buyer/seller without realizing the flash (not preflash) did not work.  Based on phone conversation the estimate was acceptable, but offer after evaluation was half of expected amount so I asked for my camera, 3 lens, battery, charger, 2 filters, and printed manual back.  I was going to use the money toward upgrading a lens for my Olympus MFT camera.  Should I consider trying to sell all items as a package locally with acknowledgement of issue to buyer, keep lens and camera and keep using.  I also thought about a used body, but I don't use flash enough to justify the expense when my read need is better lens for Olympus.  Any thoughts? Thanks.

Cutting the offer in half seems pretty harsh, but I don't know the cost of repair to them to make it sellable. I'd ask for it all back and try and sell it locally or send the body out for flash repair and see if that is worth paying for. If the cost to repair separately is much less than the half amount, it seems like it could be worth having fixed. If you were good with the original offer amount.

Not knowing any of the actual dollar amounts, it's difficult for me to say exactly what I would do though.

Take a price of a compact external flash into consideration.

Not sure what you mean by the preflash (working ?) but it seems to me you have some setting in place, which disallow your main flash  to be initiated.