For most of the business gifts that you give out you're going to want to think practical and reasonable; however there are certain situations where you need to go up, up and beyond the norm and really try to make an impression. In these situations expensive business gifts are called for. Very expensive business gifts are definitely exception to that rule, as most often you are going to need a larger quantity of smaller business gifts to satisfy a larger group of people. However not everyone is your biggest and best customer, so for those huge clients that you absolutely have to keep happy because your livelihood depends on them; dropping the extra change to get an expensive business gift absolutely makes sense.
Expensive business gifts can be anything you can think of, but ideally should relate back to what your client enjoys. This is perhaps the one and only time in business marketing that your business gift should not be promotional, but should rather simply be a business gift that your client will be interested in.
This is not to say however that your business gift can't represent your company, just that if you're gift is going to represent your company you better be sure that it is something that the client is definitely interested in, as an expensive business gift that doesn't interest your client is essentially useless. More often than not your big client will not be interested in a promotional business gift, even if it is expensive, so it is always better to err on the side of caution and get them something that they truly enjoy rather than something that promotes your business.
Picking out an expensive business gift does not need to be difficult, but it can be if you don't have a good relationship with your clients. Hopefully you do have a good relationship with your client, as a good relationship is important for more than just picking out an expensive business gift, but also just good for your business in general. There are no solid rules to follow, because it all depends on what your client likes, but when picking out an expensive business gift try to keep it reasonable.
Clearly buying them a boat would probably be excessive, however if they are really big fans of boating then you might want to give them tickets to a boat race, or a very fancy ship in a bottle, or even some antique boating paraphernalia. There really is no one good answer when deciding what to buy for an expensive business gift but hopefully you have, over the years, developed a close enough relationship with your important client that you are able to pick out a business gift that you know they will enjoy.
If you have not developed this sort of close relationship you are not completely out of luck, but picking out a good business gift will be difficult. As a rule try to avoid products that you produce yourself, and stick to generic gifts like expensive pen sets. These are not as good as an expensive business gifts that comes from the heart, but it is better than nothing.