If they ask you to pay the market fee, then you might as well buy your bike outside of C2W. Give you my example:
I opted for a £1k voucher. My employer uses
Halfords who charge me (via my employer) an 11% admin fee - total cost £1116. I pay £93 salary sacrifice, so after 12 months, I will have paid £1116. I would then expect the bike to be free. My tax & NI saving is 22% so a £1k bike actually cost me £780.
If I then have to pay a market fee of say £360 after 12 months, then I might as well not bother with C2W. I assume other schemes run similarly, so where will the benefit for commuters?