Ellen,
Keep in mind that lotto traffic is sticky to it’s site and that Bingo is also sticky.
So you will deplete a lotto site of possible players quickly, and if others are using the same site it may already be depleted. The number of bingo players you can get from lotto is finite.
Conversions from lotto places to bingo are existant but not great. Given the cost, it’s allright as long as you are using a site that still has fresh traffic.