How often EastWest releases updates that you need to pay money for?
I know they have these 50-60% discounts pretty often so I don't feel pressured to buy anything right now, but I did subscribe to the Composer Cloud. I am entertaining the idea of subscribing to it just every now and then, but it's actually pretty expensive! The $19.99/month is a one year contract. A single month costs $29.99 and that's 30% off, so normally it's about $42.71 + 24% VAT. So unless I manage to get those one month subscriptions during a sale, that's almost $53 a month.
IF they release paid upgrades something like every other year and IF I subscribe to CC about once every three months and IF I need more than one or two libraries, then it's probably cheaper to go with the subscription. But if I need just one or two libraries and I need them more often then every now and then and it takes them 4-5 years to release the next paid upgrade, buying them is actually the better deal for me.