Rakuru: Or you could just buy some trading cards off of the marketplace and craft badges. I'm not a Steam Marketplace expert, but it seems that many of the normal trading cards go for $0.10 - $0.15 while many of the summer cards are currently going for $0.50, so it may still be worth it.
The cheapest set is (usually) "Counterstrike: Global Offensive" (CS:GO). It's a 5-card set. At the beginning of the sale, the cards could be bought for 4-5 cents apiece, so it cost you 20-25 cents to craft the badge. Which netted you a Summer Sale card that could be sold for about 45 cents at that time (or about four times as much if we you were lucky enough to receive a foil card).
Needless to say, lots of people used that mechanism to create a whole army of level 5 clone accounts, in order to farm even more Summer Sale cards through voting. The ease of that exploit might have been the reason why the minimum level for the voting rewards got raised from 5 to 8.
At the beginning of the sale, there were 45,000 CS:GO cards on the market, currently there are about 18,000. The price of CS:GO cards has jumped to 10 cents now, and the price for Summer Sale cards has dropped, so it's not profitable any more unless you factor in the voting rewards that you can sell.