That's a great collection, you have there. So much Alpha Golds in one page!

And yes, you can buy upvotes using your DECs. They actually give a better return for your DEC Tokens with at least a 20% ROI.

My 2,500 DECs, for example, got me a 3.972 STU upvote. Using a rough calculation, at the current price of 0.0024 STEEM per DEC, the 2,500 DECs would have gotten me 6.0 STEEM, if I sold it. But because I traded it for an upvote, I will be getting a total value of 7.236 STEEM (3.669 SP + 1.446 SBD) at payout, instead. That's already accounting for Curation Rewards and using the current exchange rates for STEEM and SBD.

Of course, sometimes, I guess depending on the queue, I actually get higher value upvotes. The best was when my 2,500 DECs got 4.887 STU.