Most children can understand that choosing one activity may exclude another due to the limited resources available, however making them feel like a bad person because it turns out that they don't like something they thought they would like before they had tried it doesn't seem to have any effect other than to discourage one from trying new things.
In some ways I must discourage my child from trying new things - he has to somehow, and I'll help however I can, determine before we buy the necessary equipment whether he is going to appreciate the cost in terms of joy/fulfilment/health/happiness from the activity. For those super-wealthy this is obviously a non-issue.
Suppose your child wants to try running an international diamond mining corp. You're not going to discourage them by not buying one are you, you bad bad parent you.
;0)
Your suggestion only works for parents with near limitless means. If my kid took a passion for piano, say, and we bought a piano we couldn't just buy something else that year if he wanted to do something else and we'd be unlikely to sacrifice our holidays 2 years in a row to indulge him if he's going to quit. You make your bed, you sleep in it.