There are many GIS software packages out there now, so you are no longer stuck with only the couple big names in the industry to accomplish you mapping goals. If you are just starting to look at some mapping projects I recommend that you fully analyse what you are going to need as far as functionality and features that you are going to need. What kind a data analysis are you needing to do? Do you need to be able to transform or creating your data? Do you have GPS or other hardware that need to integrate with the software to improve workflow?
Features of the GIS package that you will use can greatly increase the cost of the basic package. For example with ESRI ArcGIS if you want to be able to do a line of sight analysis you will need to also purchase the 3D analyst extension which will run you $2500.00 more than a basic license. With Global Mapper you can do a line of sight with the standard license that you buy. As with choices there are some pros and cons to the different choices of software, in the previous example the final output would also need to be considered as ArcGIS might have a better looking graphic output to include in your report, but that does not have anything to do with the actual analysis you were originally wanting to accomplish.
Another aspect to look at is what hardware you might already have deployed in the field such as GPS units, cameras, laser range finders ect. For mobile mapping you will need a solution that will run on you equipment and also in the office. Some GIS software packages will include a office based software to work with your mobile platform while others will only work on the mobile device and you will need to have a different program to view and manage you data once you are in the office.
One of the ways that you could look at reducing the cost of deploying a GIS system is a hosted solution. The GIS Marketplace has many services that will allow you to try out a service before you have to put forth the effort and expense of a self supported solution. you can also run ESRI Enterprise on the cloud via Amazon. but you have to purchase the license and use the cloud hardware which could be beneficial if you are lacking IT support in house.