Hefty $ Difference Between One Way And Return Segment
 

I've been looking at booking flights to Paris and have been searching return and/or one way segments. The same leg of a return flight is $300 more than the one way return flight. I've not seen this before. Will Westjet honor the lower leg price on a return ticket? The wait time to call and ask is ridiculous at the moment. Thanks for your help.

Edit... should have mentioned that's I'd like to use my companion voucher.

Normally the return flight would be priced in CAD $ for a Canadian originating outbound flight. A one-way flight often will be priced in the currency of the origin, i.e. Euros in the case of Paris. Did you take any currency conversion into account when comparing the prices?

Unless I'm using a companion voucher, I often buy individual one way legs for European travel on WestJet. The big difference appears to be in their "Other ATC" charges, which are significantly lower for the European markets.
If you really want to save money, return flights from Europe are cheaper still, although that would likely only be practical for Canadians who travel to/from Europe frequently.

If correct, why not just buy two one-way segments?

Both were priced on the Canadian WestJet site.

Should have mentioned that I am hoping to use a companion voucher.

In that case, the return price is the one you have to work with - they won't re-price it to the 2 x one way price.

As mentioned above, the cheaper return fare option is to book your flights return from Europe. Unless you're planning a few European trips from Canada in the next 11 months (so you could embed your from Europe return in the middle), this probably isn't a viable option.