You enjoy the things you enjoy, and I'd hesitate to suggest that one choose one's pastimes based upon how inexpensive they are.
Hesitation over! Reading is the greatest cheap solitary recreation there is. Sure, you can make it expensive if you read only new hardcovers. But all it takes to have a lifetime's worth of good reading is borrowing privileges at a decent public library. In many cities, library sales, thrift stores, yard sales, and bookstore clearance sales offer lots of opportunities to get books for $1 or less. Paperbackswap lets you trade your unwanted books for wanted ones for about $3 each.
Close to home for us, the Bay Area Free Book Exchange in El Cerrito, CA exists to simply give away books. The selection includes a lot of the forgotten bestsellers of yesteryear, as you'd expect, but a lot of good stuff, too. I left with Hackers, Stand on Zanzibar, One Two Three... Infinity, and Distraction. Jen took The Grains Cookbook, The Women's Room, and Cryptonomicon.
Again, I understand that if you know you're not into reading for fun, then you're not, and that's not likely to change. But if you are, I'll remind you that the world is so full of cheap, free, or freely lent books, that reading can be not only enriching and rewarding, but dirt cheap, a combo that's as frugal as it comes.