Haha "I don't expect to make thousands of dollars...". That's funny.
10 USB Block Erupters have a hash rate of 3.36 GH/s. Assuming that the difficulty rises at a modest rate of about 22% per period (currently it is more than 30%),
your miners will mine a total of about 0.205 BTC, 0.195 BTC over the next 6 months.
At today's exchange rate, you will earn about $53.
But, let's look at it in terms of BTC. After all, instead of buy the mining gear to obtain bitcoins you could have just bought bitcoins directly. Assuming you bought the miners a week ago when the exchange rate was about $200/BTC, you could have bought 0.475 BTC instead.
Congratulations. You paid 0.475 BTC to mine 0.205 BTC.
My advice, use the block eruptors to have fun and learn.
Best advice ever