Chez at Ultimatehandyman shows the construction of a 'line bending machine' to heat and fold perspex/lexan etc. The device is very simple and the results are more than acceptable for making cases.
https://www.youtube.com/watch?v=XveHMbzbyYQ
I'm currently using floorboards - specifically 'laminated' floorboards - of the type you can purchase by the pack full from the local DIY supermarket for £10 and upwards (depends on the finish you want!). There's enough material in one packet to keep the most ardent case-maker busy for a year.
These are 6-8mm thick, cut easily with a hand saw and, if you can use a table saw with a 45 degree cut angle, make terrific cases for the likes of hi-fi's etc. Team it up with some 6mm square stock (also available in said DIY places ) or aluminium angle - for making front panel brackets - and you have yourself a sturdy and appealing case for pennies.