I was playing a game today where my treasury was filling up pretty fast, but my research rate was horribly slow. So I just ended up contacting the other most advanced AI civs and kept buying techs at fairly reasonable prices. I mean, starting at 300 gold a piece and slowly working its way up to 1000 a piece. This all ended at the start of the Modern Age, however. But by then, my research facilities were in place, and I ended up surpassing everyone in techs.