Synagogues do not pass around a collection plate, either for Sabbath services or for the High Holiday services. Thus, the process of collecting has become more formalized; often, a significant amount of the annual budget for a congregation is collected by buying a seat. I think it’s easy to interpret this practice in a negative way, when contrasted with how churches collect money. But it is not bad, merely different. It is important to view it in light of the practical need for the practice. As the previous respondent pointed out, congregations are often packed to capacity during the High Holidays, and this is one way for synagogues to limit and predict the number of attendees. As to not allowing people to worship if they don’t pay, I have personal experience of having walked into a synagogue for the High Holidays and was welcomed without having paid. So while paying for a seat is the expectation, it is not a barrier to admission. You just have to stand or sit where someone left their seat for a while!