Ask HN: Advice on seed stage valuation/cap

I need advice on whether the current valuation/cap of our young startup makes sense. We started months ago, in San Francisco, and personally put $150k of our own money. A team of 5 has worked on the company for a few months with zero or reduced salary. We are a platform to digitally handle real estate titles (to start!) leveraging the blockchain, offering an API for companies so that they can provide their services to homeowners. Think of it as, in principle, a Twilio for real estate. Our solution is fully legacy-friendly, and doesn't require any change of law, or any agreement with a county. Yes, we're focusing on the US market initially.

We are now raising a seed round of $1M, at a $12M cap. We believe the $1M is enough to build the product. We also believe that the $12M cap rightfully represents the amount of work and money already put in the company, and the de-risking made possible by these months of work. The team is quite senior, with exec-level roles at Amazon, Microsoft, Apple, Vodafone, etc.

Some seed investors have objected that we should reduce our cap to something like $6M, and possibly raise a slightly larger amount ($1.5M or so). Other than that, they like the team and the value prop quite a lot.

Do you think their objection on the cap makes sense? What kind of reasoning can be done when evaluating these two numbers (amount raised, and cap), in this particular situation?

For full context: I have invested in more than 60 startups in the past few years with a small seed fund (never lead investors), plus another 6 as an angel. I am quite familiar with the process.

Happy to get some good feedback or suggestions. I'd be also happy to share a bit more details in private, email me at $hn_username at gmail.

Thanks!