Over at the PlayStation blog you can find an entire list of games that are discounted as part of PS Plus' Double Discount sale, running until March 22, meaning that if you're a PS Plus member, you get even more money off.
The full list of titles can be found on the blog, but Fallout 4 has been cut from £49.99 to £13.99, No Man's Sky has been cut from £34.99 to £13.99, and The Witcher 3 has been cut from £24.99 to £14.99, and there's plenty more big titles with reductions. Does this justify the cost of PS Plus?