Hi .. PayPal is free for buyers unless you are paying in a foreign currency. No one sells you foreign currency free be it the bank, PP or the Post Office.
PayPal charges a conversion fee of 2.5 %. The canadian value shown on eBay is a guide only based on Bloombergs and is the interbank rate not retail.
Most conversions are for US currency and cannot be avoided unless you have a US balance in your PP account or a US PP account .