cases that open on the side are a pain when still on the bike... everything wants to fall out. they are OK if you can lay them out like a suitcase & might fit what you are doing. personally I hate them. Happy Trails has the cheapest hard boxes that are decent, but don't let them pre-drill the holes, do it yourself. Ortlieb has nice weatherproof saddlebags that don't require a rack.... not enough space for everything you need though. Wolfman has this big tube thing that looks like a good deal.
P.S. whats expensive is buying something that is crap & then having to replace it with something that works