I've been researching getting a tower..., yes they are expensive. Even the Monster Tower, once you add racks ($475) and replace your bimini (if you have a bimini, it probably won't work with a tower), puts you at about $2000...
Wakeside
http://www.wakeside.com/ has some good prices. You can get a Titan I or a Skylon X-Treme for under $1600, but adding racks puts you over $2000 on both of them. And you have to install them yourself or shell out more $$ for installation. Have you considered an extended pylon? Not as sexy, but functional. Also, one thing to consider with your boat being a 1988, the fiberglass at the mounting points will likely have to be reinforced, as they did not build boats back then with towers in mind.