I was given a Boker Infinity folding knife as a gift. A lovely knife and very sharp. I used it as EDC for about two months before it became too dull for everyday tasks. Boker will resharpen it for $13.95. That might be reasonable once a year or so, but not six times a year.
If there are no nicks or chunks out of the blade, you should be able to strop it yourself with little or no effort.
For the amount you mention, you could purchase the necessary materials and strop it as often as you like.