I don't think your question can be answered based on the information provided thus far.
This isn't a matter of "cheaper," it's a matter of what's most appropriate for the type of organization you represent. Like it or not, you WILL get the license within the proper category, or: 1) your application will not get coordinated; and 2) the FCC will return or very possibly dismiss your application with any money paid to the coordinator and (possibly, if you are not fee exempt) the FCC not refunded. It can't be more simple than doing it right or losing your money. A license - from start to finish - can cost between several hundred to tens of thousands of dollars, depending on the number of sites, specific items that need to be addressed, and whether you would need to retain legal counsel to draft waivers, etc., so there's a lot at stake.
One of the items omitted is that a frequency coordinator will assess a fee, as well. There may also be fees for supporting documentation, such as DHAAT analysis, short-spacing, Regional Planning Committee co- and adjacent channel contours, and possibly responsible radiation plots. Each of which may preclude your use of a given frequency in a given area.
The Sprint/Nextel frequencies were "given back" following rebanding, and I believe they are complete in all but the border areas (I could be wrong, I don't work with 800 on a daily basis). What that MIGHT mean for your region is that the resource has already been consumed. Competition for 800 MHz frequencies is not casual, it's fierce and the resources are usually gone to those who have filed in advance and were willing to be in queue.
Here is a list of frequency coordinators who handle 800 MHz:
FCC: Wireless Services: Industrial/Business: Licensing: Frequency Coordinators You are best advised to call several of them, ask questions relating to how you intend to use this system -- and for whom -- and pricing. Shop around and get the best value. The pricing will be in the ballpark, but could significantly vary between each.
Let me also state that you have a construction deadline once you successfully receive a license. You or your agency will need to put something on the air within that time period (meaning, you need the financial backing of being able to procure and build within that window) or your license becomes invalid and you will need to go through the entire process anew.
Good luck. Call several of the frequency coordinators on the list for facts before you commit to any decisions.