You have a working prototype. You need to ask your investors for money and explain them why you need $100k for just product development. Assuming you're first time founder, your experience with how much money you need is negligible. Don't worry. This what this post is for.
When I started out, I thought I'd be able to develop a final prototype for $10,000. It turns out, I was wrong. Even when I approached to investors and told them I have a validation prototype developed in $20,000 and just need another $10,000 to complete the development, They thought I was naïve, which I was, but at the same time was impressed with how much I was able to achieve in just $20k.
I'll try to give you a brief of where you'd spend most of your money:
1. Industrial Design.
If you're dealing with a B2B project, you may just get away with building a box of plastic. But If you're building a consumer electronic device, you need a good designer who understands your market needs. Hiring an awesome Industrial Designer becomes crucial. How to hire one? Discussion for another time.
I sent an inquiry to ID designers from around the world. India. Australia. US. UK. France.
US: A renowned ID design studio in San Francisco will cost you $200k+. A good ID studio will be in the range $50-80k. A good designer could do the job for $30-50k. It depends on what you need.
India: India is cheaper compared to US but designers have almost no experience in consumer electronics. Also, in my experience, if you're designing something for a global market, it is better to hire someone from US or France as they tend to have a better taste than Indians. (I'm not making a stereotype. This was my experience. If you're curious, buzz me to ask for the list of people I spoke to before I made this argument.) You can get a really good designer for Rs. 3 Lakhs-10 Lakhs here. (~$6,000-18,000).
Australia, UK, France: They are a lot more expensive than India but cheaper than US. Again, they have awesome experience with material selection and fashion, given all the big design houses there. But they do lack in experience with Electronic products. It depends what you're looking for but you may expect to pay a designer here $30,000-100,000 for your job.
In my case, I ended up signing with Bill Webb from Huge Design.
2. Electrical Engineering
You'll need Firmware Engineer + Electrical Engineer.
If you have these guys as a co-founder for your team, great! You can have them work for hours without paying them a penny. If not, this is where you can save some money. For your PCB design and component selection, hire some Chinese guy. No joke. You'll pay $140+ per hour for an engineer in US. You'll pay $20 per hour for an engineer in China.
In China, they could turn around multiple iterations of PCB in 1-2 days. In US, it takes about 1-2 weeks.
You may get Electronics and PCB design done in $1500 in China, when compared to $15000 in US.
For your firmware requirement, hire someone in US. People in China don't know how to code. Expect to pay about $10,000-20,000 for this.
3. Mechanical Engineering.
This is tricky part. Given on the complexity of your product, your mechanical and assembly design will vary in complexity too. For a simple box like product, $200 is enough for this job.
For a complex product, a budget of $5k-20k is a given. But this whole process will be tricky. Sometimes industrial designers will not work with mechanical design you give them. Sometimes, they'll ask for a mechanical design from you. But this is a long conversation for another post.
If you're thinking of outsourcing, there are a lot of people who could do it. I spoke to Greg Kress from Radicand for the same.
With this, you'll have a product that you could mass manufacture. Hope this 3 part series helped you get a sense of how much money you'll need for your project. If you any more questions, write to me and I'll do my best to answer your query.