Assuming bid mode means 'where I am bidding, find all cards where there is a sell price <= my current bid + HowClose' then line 73 should be changed from:
if b.text == "ask" and BidOrAsk == "bid" and float(a.text) > float(userSetPrice[index])+float(HowClose):
to:
if b.text == "ask" and BidOrAsk == "bid" and float(a.text) <= float(userSetPrice[index])+float(HowClose):