I haven't done the calculations in years, but when I started about 15 years ago, the initial cost of equipment paid for itself in about ten boxes of shells. After that, whenever I bought a new caliber gun all I needed was a new set of dies, so it only took about two boxes to pay for the dies.
You have to decide how long it takes you to shoot ten boxes of shells.
The two main points, as mentioned above, is that you will shoot a lot more and therefor become a much better shot. It also gives you the flexibility to use more rare (and therefor more expensive factory load) calibers. For example, I think the 260 REM is the perfect cartridge for Tennessee whitetails, but the shells cost about $40 a box in the store, if you can find them. But I can reload them for the same cost as a 243 WIN or a 308 WIN.