edit: after much googling I found this comment:
does this stand up with regards the pi?Short answer: if your site is efficiently configured, the cost of compression is... zero.
The key is memory caching. Without it, Apache has to process each file request by getting the file from disk and running it through filter modules, such as mod_deflate. This requires disk I/O and compute time. Instead, use a memory cache to store the results after compression. The next time the same file is needed, Apache gets it from the memory cache. No disk I/O. No compression CPU time. The cost of disk I/O and compression is now paid only the first time the file is requested, not every time.