It depends what you do and at what scale.
'Hardcore' software :
Mentor DxDesigner/ Boardstation , Cadence Allegro ( PCB design )
Agilent ADS , Eldo , Analog Artist ( spice simulation )
Hyperlinx, AST studio ( field solvers for EMC )
Flomerics ( Thermal modeling )
Synopsys , SpecMan , Modelsim ( HDL synthesis / verification )
High end software :
Zuken CB5000 , Altium (PCb Design ) , OrCad, Mentor PADS
Quartus (paying version), ISE (paying version), Modelsim Lite , Veritak, Aldec ( HDL synthesis )
the difference between modelsim and modelsim lite is that they artificially slow down the simulator and things like compute farm runs are disabled. you can do the same thing but just much much slower. things that take the paid version 1 second to run take half an hour on the free version ... then again... by the time you need half an hour runs you're playing with thousand $ FPGA's.... or trying to do timing closure on an asic ... and then you have money to spend on tools anyway.
Hard-core is not bought but leased. every year you need to fork over more money or it stops running.... My division of the company i work for spends a couple million $ every year on Cadence licences...