I buy and sell on ebay. I have been buying plants this Winter and they have all been shipped priority from all across the country and I only had one arrive in poor condition. Fortunately that was a moss and even though incased in ice it was alive!. Non of my plants have had a heat pack. On the selling side I have been selling snails and some plants from here in northern lower Michigan. I do use a heat pack for those and all have arrived alive and well. Insulated boxes of course. On occasion I have held shipment until temperatures improved on the buyers end. I have not sold shrimp or fish yet. Once it gets into the fifties I will start selling those.
I have purchased fish numerous times on ebay and all have come in very well. I do look at feedback to determine if issues were resolved. A seller does not have to have 100% positive feedback for me to buy from them, when it comes to fish, because I know some buyers are never satisfied. As long as the seller tried to make things right I will buy from them. Also keep in mind some totally reliable sellers are on ebay, like Wetspot. In resent years they have been one of my most trusted sources but I would normally just call them and pay for overnight shipping. Some fish are worth the extra dollars!