Unlike some other ASIC vendors, BFL products are priced in $US not BTC, how you come up with those $US is up to you.
You're far far away from truth.
1. BFL products are priced both in USD and BTC. You can see the proof on the commercial invoice BFL issues to their customers. The official document for every purchase is the INVOICE:
2. How I "come up with those $US" is exactly NOT my choice but BFL's choice, because customer acts entirely upon BFL instructions how much bitcoins to what bitcoin address they have to pay!
If you choose to use Bitpay instead of Paypal because you want to convert some BTC to $US to pay for the item, then what happens to the BTC after Bitpay receives them is no longer your concern.
1. If I choose to use PayPal I have to be PayPal customer! Customers paying in BTC don't choose to use BitPay. BFL made this choice. BFL customers are not BitPay customers for they don't sign any contract with BitPay to be their customers. BFL signed such a contract with BitPay to be their customer.
2. You are correct that once BTC are on BFL's bitcoin account with BitPay customers don't have any control over them. Reason for this is that transactional currency is BTC not USD. As we all know refund is nothing else but a reversal of a transaction. This is why BTC refund must be in BTC not in USD.
3. Bitcoin refunds are treated by BFL as if customers didn't purchase ASIC but USD. This is a blatant violation of all forex regulations. Neither BFL nor BitPay have been licensed to make currency conversion for BFL customers. They are not regulated as exchanges.
The BTC price is generated as a spot price by Bitpay not BFL, as the bitpay.com URL at the top of the page would obvioulsy tell you if you hadn't deliberately left it out of the picture. I have a Bitpay merchant account, I know how it works.
If you don't have a PayPal account then bad luck, they are the two options on the checkout. To pay any other way you would have to contact BFL and arrange it, eg they accept bank transfer.
Once again as the purchase price is in $US your point about forex is not valid.
I don't own any $US, it's not my local currency, for me to pay BFL I would have to convert to $US generally using PayPal, and if I wanted a refund I would expect to have to convert back from $US to my local currency myself, regardless of what happened to the exchange rate in the meantime. If my local currency was BTC I would expect the conversion to use the spot exchange rate, not some past exchange rate.