Anyone explain why same destination have two price differences?
 

https://www.google.ca/flights/#flt=Y...038*.USD.29038

$291 YVR-DFW-MIA on a thursday, MIA-DFW-YVR on a Friday

yet

https://www.google.ca/flights/#flt=Y...303*.USD.73135

for the exact same route/flights but clicking on 'round trip' is charging $732 , YVR-DFW-MIA on Thursday (exact same arrival/depart), MIA-DFW-YVR on Friday.

Is this how you book cheap flights for mileage runs? Simply manually select ever stop and you'll get a cheaper flight than the rigged 'round trip' ?

Happens from time to time when the airline tries to force married segment inventory on itineraries. What's interesting about this one is that forcing the separate segments isn't pricing separately (ie both still price YVR-MIA + MIA-YVR) rather than YVR-DFW+DFW-MIA...) but it is changing the available inventory on the flight. The expensive version prices into L on the outbound and K on the return. Forcing the routing in the booking engine drops both into Q.

I've experienced this fairly often on complex TATL itineraries (3 stops each way). Breaking up the itinerary at different points would split the open inventory while still charging the same route overall; i.e. SJJ-SRQ would always be charged as SJJ-SRQ, but the inventory (and hence the price) depended on whether you'd break it up as SJJ-ATL-SRQ or SJJ-ZAG-SRQ or SJJ-CDG-SRQ. This was on DL/AF/KL ticket, though, and the price differences weren't all that big (within a couple hundred $). Splitting it up completely (SJJ-ZAG-CDG-ATL-SRQ) gave me the best price about 50% of the time - so breaking it up into segments won't always give you the best price.