Matched Tubes do I need them and why?

I have purchased a tube pre amp that has two 12aux7 and two 12 au7's for tubes. I would like to upgrade these an am wondering, do I need matched pairs of each? or do I just need to by new ones. I can get new for about 20 bucks, but have been quoted 110 for matched.

Please let me know what ya think and my apologies if this has been discussed before. Not much time to surf these days.
Thanks for your help.