It's a polite and friendly way to say that you are happy to do something, usually in response to a request or invitation. It implies a sense of familiarity and warmth in the relationship.
Here are some examples of how it can be used:
* "Te ayudo con el gusto de siempre." (I'll help you with the usual pleasure.)
* "Nos vemos mañana con el gusto de siempre." (See you tomorrow with the same pleasure.)
* "Gracias por la invitación, iré con el gusto de siempre." (Thank you for the invitation, I'll go with the usual pleasure.)
It's a phrase that conveys a positive and welcoming sentiment.