All of the WTCR seasons have been brought up to the same spec and BoP'd. So any WTCR events I run in the club will use all three packs together, to allow the maximum number of people to join at minimal or no extra cost.
They're not making things up as they go along. Each user can only buy each pack once. If you buy the Premium Pack you get everything in the game at that time for one price... a pretty good deal, which gets better each time they release new content since you get more for the same price. After that you have to buy things individually, which I don't think is that unreasonable to be honest.I was hoping, having bought the ultimate pack in November, that the new content would be cheaper by dint of discounts. Seems not so maybe I have to wait until enough comes out to make the ultimate pack available to me again.
It seems to work like that for some things but not others (gt3 pack, pro pack for example) which is a bit annoying as it feels like they make it up as they go along.
What you can do if you're adamant to save money is keep an eye on the content included in the Starter and Pro Packs. Sometimes they change it, so it they happen to add something you don't already own you can buy one of those packs to get it discounted. But as above, you can only do this once for each pack.
You can also wait for one of the numerous sales which happen each year, with the next likely being at Easter which is only a weeks away right now.