There's a sale on the UK and US PSN stores, with (up to)double discounts for PS+ members.

For example, Trials Rising is 25% off(£29.99 -> £22.49) but 50% off for PS+ members (£29.99-> £14.99), whereas ONRUSH is 80% off!

There's a bunch of VR stuff, too. Some games have an extra discount but not necessarily double.

I guess it should work for free trial memberships, too, but if you save over 6.99 then you could just buy a month of PS+ to benefit.