If you are looking for a chat-based solution for sales, marketing and support with extended audience segmentation, then check out http://insent.ai/. Full disclaimer - I'm the founder

If you want knowledge repo, chat etc, HelpScout, Crisp.chat are good. Chatwoot is also good. For advanced chat support use cases, Ada is good, but very expensive. If it is B2C use case, Manychat is good too.

If you want marketing automation, CRM, product tour, knowledge repo and chat, then I'm afraid Intercom is your best choice. It starts small, but gets expensive very quickly though.

Depends on what you're looking for in the alternative. If it's just the live chat functionality, Tawk.to and Crisp.chat are good options. On the open source side, there is also Chatwoot and Chaskiq.

If you want a more full-blown option with some CRM and outbound, Hubspot (generous free tier) and the open source Erxes are both great.

Really would like to see some viable alternative in terms of ease of use and customization. I do feel intercom still shines with the combination of all 3. Would love to see an OSS / cheaper startup friendly version here which works as well

Check out Happyfox - they have chat and helpdesk products quite competitively priced.