I have always used cash, don't know about credit cards. If by any chance you can still sign up for the convention, even if it is costly, it is worth it, the demos, probably cost $8.00 each, are well worth it. On Thursday night, at least last year and in other years when I attended, they have a vendors showcase, where the vendor are showing their newest product, a great time. Try to figure out what you would like to purchase while at the convention, by checking our the various vendors sites on line, prices are frequently less then normal. Take at least twice the amount of money you think you want to spend, three times even better, because you are going to find so many things, you don't really need, but can't live without.
If you actually go to the convention, you will be able to meet other decorators, they have a first timers meeting, that will introduce you to other first timers, they will tell you about the convention, you will get a hospitality bag, when you sign in, or a ticket that you can exchange for the bag, with some free samples, of different product, information about various products. Lots of goodies.
If you can't go to the convention, then yes the $50.00 is well spent, but there is no way you can really see everything in just one visit to the vendors room.