That really depends, it's not a given.

My last sale booking costing c£1.5k and will net 20k Avios. I had an extremely wide range of destinations and time period to choose from.

A hypothetical (there was zero availability for my preferred destinations) Avios booking would've cost me c£700 and 100k Avios.

Unless you are short of cash or really value the refundability (not flexibility, as that implies having availability to rebook) , I'd argue that current sale pricing model makes Avios poor value for premium cabins.

I use mine almost exclusively for RFS in economy for this reason.