I received similar advice a couple of years ago and I balked at it at first as well. I realize now that it is sound advice. The reason I found it to be be sound is what I think all of us appreciate as Bonsai is the beauty of a finished tree. So by having a more advanced tree, instantly you have one that you can truly appreciate and can proudly show to those that visit. It doesn’t need “time”, and in the end time is what you have paid for. It may not need a great deal of work from you in terms of styling but it will require you to tend to it’s needs…in the end that is the most important. It will teach you to listen to your trees needs and how to provide (water, nutrition, protection from weather, temperatures, pests, light requirements, what to do when you are away on holiday) because you have a vested interest in this tree in terms of money. It is much easier to let something inexpensive go by the wayside. In the end you will likely spend less money buying something of greater value than a bunch of starter trees and nursery stock, and pots, and soil components, and then tossing them in the bin after a few years because they have not really become what you wanted or, you have run out of space, or they turned out to have other problems.
I would also advise to join a local club. Joining mine has been paramount in this journey. Most have an annual auction who’s proceeds benefit the club, and you will have the ability to purchase other members trees, collected material, or workshop stock at far less than you would at a retail store. Clubs are likely to have workshops with touring artists and quality grown bonsai stock available to purchase and you can participate in a live demo…in a single day you can create a very finished looking tree with the help of a professional and other club members for a fraction of what it would cost to buy the same tree. These then become your starters and are far better than you will find at the nursery and do alone. You can also gain friends and knowledge, often discounts at local Bonsai retailers too.
So maybe hold off a year on the expensive tree and test the waters while you save a few bucks. Join a club, and keep what you have alive. Have fun cutting and styling and the like, knowing that what you have now may not hold your interest in the long run, but let them teach you how to keep them healthy. If you feel like you still have the bug then take the big step.
Just my 2 cents. Bonsai on!!