Ten year old models - those can and should be pretty good kits and won't necessarily be on sale - most likely sold out.
As a rule of thumb when shopping for kits online, try to source the brand from the region they originate from. For example, Tamiya should be cheaper from Asian based webstores, like HobbyEasy or LuckyModel. Similarly if European brand, try to pinpoint closest to the particular country, or at least west or eastern Europe. Of course, always shop and compare, as not every online shop fits this guidline.
Another good online shop is Spruebrothers. They have a daily 'deal of the day' for a few products, but not always kits. Also sign up for their newsletter, so you get notified of specific sales.
regards,
Jack