Ambrosia is a fondant. Can't see the point of paying it's price as making your own is easy if you only have a few hives.
Ambrosia is actually just a collective brand name for the various bee feed products produced by Nordzucker in Germany.
They have syrups, fondants, and powders.
Similarly the bigger brother and market leader in the trade, Sudzucker, make Apiinvert, Apifonda,and Apipuder.
Other sugar companies have a similar assortment. Most fondant is made by Sudzucker or their subsidiaries, or by Belgosuc, and just packaged in the branding of other companies. (I have visited two plants in Belgium, one of which is a Sudzucker plant making most of the fondant brands sold in the UK which you might think to be British makes, and seen that happening) The difference between Ambrosia fondant and Apifonda, at least at the time I visited the plant, was nothing more than which roll of plastic preprinted film they had on the machine.
The specialist bee fondants do vary slightly from the standard bakers fondant, being manufactured in such a way as to have a smaller crystal size. the theory is that this aids direct ingestion rather than reconstitue to liquid then ingest. The way in which we feed fondant in this country, and the climate, probably mean that the extra money is not worth paying. ( have used many tonnes over the years of standard bakers white fondant and special formula types............not a scrap of a difference )
Getting a box or two of white fondant from your local bakery, or from their wholesaler, is the easiest and usually most economic way to go for small purchasers. Making it yourself? Well their are plenty of anecdotes about it being just as good, but I remain unconvinced of this. Hmf in home made product is always a risk, and hmf is toxic to bees, albeit that in fondant it will be at modest levels. Bees will tolerate it and prosper most seasons, but, if it ever does, your trouble will come in a cold winter with a long period with no flight.