Elegoo Upgraded 37 in 1 Sensor Modules Kit $31.45 (Was $44.99) + Delivery ($0 with Prime/ $59 Spend) @ ElegooAU via Amazon AU

Here's one for all those electronics buffs (like me) who like to fiddle with Arduinos. This updated set (I think they just removed the mercury-switch but I may be wrong) has 37 sensors and has a downloadable PDF tutorial with projects and code. You should be able to use these same sensors with a Raspberry Pi and different code. Currently 30% off making it cheaper than AliExpress and as it ships from Amazon Australia you won't have long to wait for delivery.

I'm unsure how long this price will last.

Note that this kit contains sensors only so you'll need your own Arduino (as it's not included).