Cat 5 no longer exists -- it has been replaced with 5e. However there is also a new augmented category 6 that was developed to support 10GBASE-T (10 gigabit transmissions over twisted pair – much less expensive than over fiber). There is also category 7/class F that has been a standard since 2002. Which you pick will vary based on your individual needs, however, no one expects 5e to remain a long term solution. The biggest problem that you have with cabling is that it is supposed to be in the wall for 10-15 years and support 3 or 4 generations of electronics. So the single biggest factor is how long will you be in your building? The cost is different for each grade, however, labor is very expensive especially when it has to be replaced. If you plan on adding 10G to your network anytime within the years that you want the cabling installed (some companies even keep it longer than 10-15 years) then you will want a 10G solution.
It is also important to note that copper prices continue to increase. So on top of a higher labor for tear out and replacement of a lower performing solution, the component cost for the replacement is likely to be higher if copper continues to rise (about 300% this year alone).