When to buy in and become a member?

I recently moved to a new city with only two synagogues, one reform and one modern orthodox. I went for a service at the modern orthodox one and really liked it. But they emailed me after and really pushed me becoming a member and said once I became a member I could attend future services. I attended services free at my old shul for six months before becoming a member and no one pushed me to do it. Now I feel a bit weird about this one. Is this normal for them to kind of exclude you from returning unless you become a full member?