I'm sure the aff.signup/non aff.signup ratio varies a great deal from sponsor to sponsor.
Some sponsors are very temperamental & frankly duplicitous as well, in regards to their aff.progs. - I've had a sponsor complain that her aff.prog was more trouble than it was worth & that she got 90%+ of her sales through her own efforts. Then she got a professional into manage her program & it swiftly became evident than in fact that she relied very heavily on affiliate generated sales.
Other sponsors however are far more appreciative.
This is a quote from an email I received about this time last year.
Hello Geri,
We noticed your sales for ****** have been well up this past week and wanted to express our thanks and admiration. Is there anything we can do to help you? We had set you up with access to the member's areas so you could select content for your site[s] -- is that still working? We have been trying to revamp and expand our affiliate support but we're also trying to redesign and recode some of the network and it's been very slow going. But if there is anything that would help you, please don't hesitate to ask. Your support has been a bright spot in an otherwise somewhat challenging year.
Thanks so much,
Robin
This was from sponsor for whom I now generate sales on a daily basis

I don't think they rely on my work to keep them in business, but I'm sure my contribution is much appreciated.