Depends on the service and situation of the end-user, although there can be charges at the wholesale level. For example, if you move from ADSL to an FTTC line then most gaining ISPs will have to pay a PCP Only self installation charge of £45.92 +vat. However if it's a direct FTTC to FTTC migration on the same platform then I think the ISP to ISP charge is just £2.99.
Other things, like new installs and speed upgrades also attract a cost. There can be lots of different costs so it depends what specific service and end-user situation you're asking about. Most ISPs will of course design a simple pricing structure (e.g. monthly charges) so that you as the end-user never have to see all of this background complication.