Shipping rates on site always lower


First time poster, apologies if I'm made any errors here.

I've bought a decent bit, only an occasional seller. One challenge I find on the site is that the calculated shipping rates are so far off from what Fedex/UPS actually charge me. (typically charged almost 50% more, so nearly $300 when the site says $200). There are no additional charges that explain this, as I've had both shippers break down the costs of things like insurance etc. I've experimented with a host of local shipping places in the big city I live in, and honestly YES the different locations do seem to charge me different, and categorize things differently. But all are still way, way beyond this magical number Audiogon comes up with -- like $200 for shipping speakers. Ha!

Am I missing something? I don't need to be told to do a workaround, I need to know what the formula is I'm supposed to use in that workaround. Honestly buyers are very adamant -- if I try to tell them shipping will be more and offer them a flat rate $20 higher to cover even a % of this discrepancy, they act like I'm an 1800s medicine show, trying to pull a fast one on them. I'm just trying to only lose a small amount of money on shipping.

Any insight, beyond the obvious?
marjon
Not a big trader myself but I agree, I've been burned the most on estimating shipping chares. The only safe way is to "Pad" the estimate when you charge the buyer and then refund any excess when you ship the item.
I don't have any magic formulas. But welcome aboard. Shipping is often the hardest thing about selling. Even the shipping calculators often don't get it right. I bought a preamp from a seller which was faulty. Seller was very good about it and paid the return freight. He had paid $85 shipping to me. Yet shipping back costs $105. Of course he hesitated so I did eat about $5. But he was a very good seller with customer service better that what I gat from many businesses today. Its hard to understand why one way costs more than the other
I think that the pandemic has made shipping estimates and service guarantees all the more difficult.  Maybe things can get back to something close to normal in the months to come.