Epoxy resin isn't ever cheap, that's for sure. If you don't need much, some companies do have smaller kits, like Ecopoxy. I'll probably be ordering from them soon, as this is one of the only companies that I know of which have a UV Resistant Epoxy.
If you have a tight budget, you might want to try a polyurethane clear coat like Krylon Clear Polyurethan. I've never used it for sealing concrete though, so I don't how well it will hold up long-term.
If you have a tight budget, you might want to try a polyurethane clear coat like Krylon Clear Polyurethan. I've never used it for sealing concrete though, so I don't how well it will hold up long-term.