Cyrillic extension cost

Hello experts,

I have a client interested in a cyrillic extension to one of my retail fonts. I have long been wanting to get into Cyrillic, and now I could also get paid, which is great of course, but I don't have a clue what to charge. Any ballpark estimates would be greatly appreciated.

Some details:
- six masters, three of which italic
- a 5 year exclusive license (for cyrillic only)
- just basic cyrillic, nothing obscure
- I like the job for more than the money, so I won't charge too much, and I definitely don't want to factor in the extra time needed to learn the ins and outs of cyrillic.
- no hinting

All the best,

Jasper