I have invested $70k, and spent around $15k so far over the last few months.

I am a unique case because I am also applying for a E2 Investor visa, and $70k was the number recommended by my immigration attorney to satisfy the visa application. If I didn't have that requirement I would have spent less on legal fees and hopefully would have launched the MVP for around $10k. I still haven't launched, but am about to start a closed beta program.