I think I paid 149 for my Illustrator CS4, 99 for the Corel Draw graphics suite X5. Even direct from Corel its 99.00. Alot of the free trials you see will link up to buying the software, so its complete. The main thing you want in a program is easy view scale. Draw a simple rectangle any size, pick it, then go right to the decimal scale and enter your sizes. Moving the artboard to center at zero allow you to just punch in positive and negative numbers to work off the center. Rounded rectangles are good in fab too, just need to put in the radius and its drawn. Definitely dont need to get the latest and newest software, just finding one with a forum like this to ask question if its no longer supported will be helpful, but most things are easy enough to search thru their help..
All the new stuff is great if you are using for graphics, drawing, animations with so many one click options to 3D stuff, but its never gonna be used with a standard cutter plotter. I would just do an ebay search for older software, preferably new in box though. Illustrator allows two computers to run the software so if the program is active anywhere it just wont work. Flexi 10 has a usb key you need to use when the software is working. At least that way eventually you might find a cheap version to try if you dont want to download a sample software.
all I know is most plotters just want the work saved either in AI, PDF or EPS formats to work. Thats really the only thing you need to lock up with the plotter you choose, make sure your program will save the file correctly.