Before making comment that you claim is false I went to our team management panel and exported full history for our team since 2016. It's not super active team we have, but it's still 20MB of logs in JSON and 64939 messages according to simple grep:

   grep '"text"' "./VCMI Slack export Mar 12 2018" -rn | wc -l

It's team with open registration so it's would obviously be impossible to ever pay for it. After all it's open source project.