Clearance price down from $199. Only includes 2 RF sensors (LA-5564) but I'm not sure how much each additional unit will cost as I couldn't find on their website.
They also have a basic 2 zone kit for smaller premises only $15 here:
https://www.jaycar.com.au/2-zone-alarm-kit/p/LA5480
It's a DIY installation of course.
Some further info from product page:
Fully configurable and programmable, these alarm kits give you complete control over a professional system for home or business. Each comes with a central controller and the sensors you need to get a basic system up and running, then you can add sensors and functionality as required. Up to four remote keypads can be installed at up to 100m range and each can be named for easy identification. Each user can be programmed with any of four access level codes. Any zone can be programmed for security, PA, fire or 24 hour tamper and can be fully or partially armed. All the engineering codes and memory functions are protected by a non-volatile memory in case of power failure.
Features:
• 10 programmable zones
• 4 access levels
• Walk test mode
• Events memory in keypads
• Programmable timers for entry, exit and alarm duration
Kit comprises:
• 1 x Control panel
• 1 x Remote LED controller
• 2 x PIR sensors
• 1 x Reed Switch
• 1 x Bellbox
• 1 x 50m 6 core cable
• 1 x 12V 1.2Ah backup battery
Sensors and accessories: Available seperately
• LED Remote Controller Cat LA-5561
• LCD Remote Controller Cat LA-5563
• PIR Sensor Cat LA-5564
Sensor: https://www.jaycar.com.au/pir-sensor-for-la-5560-62/p/LA5564