I think what you heard about ws the "Determine our own discount" sale aka DYOD. For a cart worth 1000TP, it gave a 10% discount; for a cart worth 2000TP it was 20%, and for anything above 3000TP, 30%. Each account could use this sale several times, up to 10 times, I think. This sale used to happen once or twice a year and one of those occasions was usually around the Anniversary event in April. I don't recall a DYOD sale last April, though. I think it was something more generic like 25% off the entire cart once per account.
It would be very nice to have a DYOD sale again this April. There is a couple of costly items I have an eye on myself and the last one has been woefully long ago.
When planning your cart for a potential DYOD sale, keep in mind though, that certain items can only be put into the cart once per purchase. For example, you can only put a single tier of Shared Storage into any individual cart or a single Universal Tool Kit. If we get any kind of sale that can be used several times per account, good planning as to which character purchases what for the account (on top of their per-character purchases) can go a long way towards saving TP.
German, female, migrated from CodeMasters in 2011, Premium member, slow-leveller, pure PvEer and opposed to Forced Emotes - wherever I fit into the statistic, it's not in its middle.