I'd charge a standard consulting fee for the effort involved in rebranding and building the client's version of the app and charge them $.66 (your price - apple's cut) per download for the lost sales.
Now, if you think one of the following may be true:
1) there may not be many downloads
2) there may be issues getting paid regularly
I'd get a lump sum to cover the lost download revenue.
The marketing campaign should have a targeted # of impressions (i.e. downloads) so you should be able
to get that number from your client and multiply
by the $.66 to come up with the lump sum.
If you want to take Aqua_Geek's approach which
doesn't take into account your lost income going
forward I would see if I could add a differentiating
feature to the original app and release it soon
after their version of the app goes live, this way
there is a reason for someone to purchase your app
even if they have already installed the other one.
EDIT: fixed some grammatical errors and removed some duplicate information
Comments
I'd charge a standard consulting fee for the effort involved in rebranding and building the client's version of the app and charge them $.66 (your price - apple's cut) per download for the lost sales.
Now, if you think one of the following may be true: 1) there may not be many downloads 2) there may be issues getting paid regularly I'd get a lump sum to cover the lost download revenue.
The marketing campaign should have a targeted # of impressions (i.e. downloads) so you should be able to get that number from your client and multiply by the $.66 to come up with the lump sum.
If you want to take Aqua_Geek's approach which doesn't take into account your lost income going forward I would see if I could add a differentiating feature to the original app and release it soon after their version of the app goes live, this way there is a reason for someone to purchase your app even if they have already installed the other one.
EDIT: fixed some grammatical errors and removed some duplicate information