Since we work predominantly with service providers that take open-source approaches, we would be remiss not to plug that as an approach here. It's taken by a significant percentage of the industry. No, open source is definitely not free. But to those accustomed to a Broadsoft-type experience, I think there are a lot of misconceptions about it that stem from a lack of familiarity with how to approach the open product ecosystem. There's a perception that it's "highly technical" or, "Okay, I got FreeSWITCH to compile. Now what?" In reality, there are _lots_ of "packaged" answers to this problem, if you're just willing to look. If you don't want to build anything yourself, there are many good commercial systems built on top of an open-source technology stack. They cost some money, but nothing on the order of the big brands, and are competitive and growing in the larger operator and enterprise markets. Example: https://integrics.com/enswitch/ It's built on top of Asterisk, Kamailio and MySQL, but very turn-key. If you have the engineering core competency to build something yourself, the ROI is excellent. Yes, there's a cost and a GTM lag, but once you sink the cost, nobody's going to hit you up for $MEGABUCKS for another 100 seat licences ever again. And again, it doesn't mean you have to write a million LOC multitenant software product yourself. There are lots of people on this list who provide hosted PBX with Asterisk or FreeSWITCH and have not had to do this. There are many approaches; you can certainly roll a home-spun multi-tenant platform if you really want to, but you can also sell individual instances of ready-to-go PBX distributions to customers inside a virtualised or containerised environment. In the latter, the port density / unit economics relative to hardware are excellent. You can put 100+ such PBXs on a single commodity box. Automating deployment with all the tooling out there these days isn't that hard. A lot of the tools already exist in FOSS land, if you just look around. And you can use feature-rich (and easy white-labelled) PBX distributions such as FreePBX or FusionPBX out of the box. Just Google around. The companies who have put a little bit of work into this have definitely forked out some CAPEX (mainly engineering time or consultants), but their ongoing OPEX commitments are comically low, and accordingly, their gross margins and cash flow are that much the better for it. What's more, the sunk cost tends to be largely fixed, so your ROI gets better and better with subscriber growth. It's not for everyone. Some organisations are sales-heavy cultures best suited to selling cookie-cutter products and don't want to do anything nerdy, or can't. But there are lots of people on this list making excellent money with open source, and I count some of them among our customer base (though we are not in the C5/hosted PBX platform business). -- Alex -- Alex Balashov | Principal | Evariste Systems LLC Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free) Web: http://www.evaristesys.com/, http://www.csrpswitch.com/