Ask HN: When to inform users that service isn't free

We're creating a service/market place which will involve companies quoting personalised offers for consumers. The product they are quoting for is a high ticket, low repeat custom item. We will require our users to pay a small token amount for the service as the companies need proof of a valid and interested lead (we're aware there are other ways to prove a lead, but for various reasons a token payment is best).

There are a number of competitors in our industry who provide a similar service, but the lack of any decent qualification means it doesn't work out for either parties.

We aren't sure whether to tell users it isn't a free service before they start giving their order details (which is a fairly lengthy process) or after they've filled in all the forms and shared their details/order.

Arguments we've thought of for telling users after they've filled in i.e. announcing it's a paid service and making payment the last step in the process):

+ Time invested in user filling out details may mean conversion rate is higher

+ Social proof contained at footer of each step in the process may create excitement/momentum

+ Trust/enjoyment of experience is built along the way

- Perceived negativity on brand/experience over hiding the cost

- Bait and switch style

Arguments for announcing it's a paid service on landing pages i.e Users aware immediately it's not free

+ More space to explain why it isn’t free

+ Upfront and transparent explanation of the process

- Exit rate will likely be higher as people immediately see it’s not free and leave

- If landing page bounce rate is higher then PPC quality score may be lower

I'd be interested to hear people's thoughts on which is likely to convert better. Obviously we'll A/B test both, but are debating which to soft-launch with.