You're not wrong to think Tailscale is primarily a software company, and yes, salaries are a big part of any software company's costs. But it's definitely more complex than just payroll.
A few other things:
1. Go-to-market costs
Even with Tailscale's amazing product-led growth, you eventually hit a ceiling. Scaling into enterprise means real sales and marketing spend—think field sales, events, paid acquisition, content, partnerships, etc. These aren't trivial line items.
2. Enterprise sales motion
Selling to large orgs is a different beast. Longer cycles, custom security reviews, procurement bureaucracy... it all requires dedicated teams. Those teams cost money and take time to ramp.
3. Product and infra
Though Tailscale uses a control-plane-only model (which helps with infra cost), there's still significant R&D investment. As the product footprint grows (ACLs, policy routing, audit logging, device management), you need more engineers, PMs, designers, QA, support. Growth adds complexity.
4. Strategic bets
Companies at this stage often use capital to fund moonshots (like rethinking what secure networking looks like when identity is the core primitive instead of IP addresses). I don't know how they're thinking about it, but it may mean building new standards on top of the duct-taped 1980s-era networking stack the modern Internet still runs on. It's not just product evolution, it's protocol-level reinvention. That kind of standardization and stewardship takes a lot of time and a lot of dollars.
$160M is a big number. But scaling a category-defining infrastructure company isn't cheap and it's about more than just paying engineers.