Honestly CAD 2,500 seems very cheap. As another poster replied, for that little I am guessing you will not get personalized attention from a lawyer, rather some assistant who is just a paperwork filler and can't answer any question except the most basic ones. Flat fees are always suspect because most good lawyers charge by the hour.
You don't need a lawyer to apply for the FSW program. However, for peace of mind I wanted a lawyer to advise me, review my documents and tell me about backup plans in case FSW doesn't work. I also had a personal situation I wanted to know how to deal with on the application. I had several detailed phone conversations where we went through every question on every document thoroughly. Maybe you don't want to do that but I wanted to. By the time the process is over, I think I will have spent about CAD 20,000 on my lawyer.
If you have any worries how to deal with a particular situation on the application (such as you are missing important documents, you have previously been arrested or denied entry to Canada, anything that might raise a red flag), it's a good idea in my opinion to ask an actual lawyer (not assistant or paralegal) for advice.
