[cissou]

it could cost more than 8bn to build one, and would take time too. Slack is right there, already built.

[AngrySkillzz]

If it costs you more than $8bil to write a chat app then you're doing something wrong.

[trott]

I'd like to know what people think developing something like Slack should cost, and why MS thought $8e9 was a potentially reasonable valuation.

[st3v3r]

Keep in mind that the acquisition value is not just the code. There's also the brand, the userbase, the engineers, and not having to actually do it themselves.