hmm yeah i'd be happy to pay 50% off their first year. Seems about right.

It seems to be the standard, 50% of first year for a single client

But then you get companies that are offering clients in bulk.

You need to do some creative structuring before you make an offer on that type of deal, because You can almost bet that at elast 2-3% of the clients you aqquire will jump ship when they see they've been sold out to someone else.

I would put that number higher than 2-3% honestly. Even if they don't jump ship right away, there's a very good chance of them leaving if anything goes wrong. Dotable is a pretty good example -- if you check the testimonial section on their forums you'll see a lot of clients leaving after UK2 took over.

OT: 50% of the first year is reasonable. I have seen much higher rates though.