"Just cannot escape the cost of converting US to CDN $."
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Since most sales on eBay take place in US$, sellers have the option to convert into Canadian dollars or use those US$ to pay for their US$ expenses (such as eBay fees for example) or US$ inventory purchases (if applicable) without wasting 2.6% conversion fee to PayPal or 2.0% to 2.4% at a commercial bank.
"All of this movement of money, US dollar accounts in US or Canada will become redundant."
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I will maintain my US$ account in the USA as it is beneficial for me to do so. While it may not apply to you, many sellers benefit from maintaining accounts in US$.
For example, every month I pay my eBay fees (generally around US$1,000 a month) with my US dollar denominated credit card. That is how I avoid paying a conversion spread on the fees. Those savings add up to over $300 a year, not to mention I get airmiles on my eBay fees and an extra 30 days to pay them! I pay my US$ credit card with US$ transferred from PayPal (or received from buyers by way of cheques/checks or money order or cash).
Many sellers here run a real business where eBay is only part of the overall marketing effort. Customers outside eBay will continue to pay by means convenient to them - away from eBay's paranoia and greed.
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