When I joined my first club (a "market price" club) I was so excited to join I paid the first guy I talked to his asking price. I do not recommend this approach ;-) The club was great and I definitely got my money's worth out of being in the club, but when I sold my share I only got about 70% of what I paid (granted, that was 8 years after joining.) My share was priced to move, but it still took me 6 months to sell.
The club to which I currently belong is a set price in/out club. The club buys the share from a departing member and new members then buy their share from the club. I FAR prefer this option, even though compared to my last club the buy-in was more expensive, because I don't have to mess with trying to sell my share OR worry about having over-paid when I bought in.
In a situation where the prices aren't fixed by the club, I see no reason why you shouldn't offer below asking price. Each situation is different but you could try to find out what a couple of potential sellers are asking, then offer each of them 70-80% of the lowest asking price (or less if you're comfortable with that.) After all, people often set their price based on what they paid, even if others shares have recently sold for much less. So the market price very well could be below their asking price.
If a potential seller thinks your offer is too low, they can counter, or not sell to you. If you don't need in the club *right now*, nothing wrong with letting your offer age for a while. You can always reach back out in a couple of months to see if a potential seller feels differently. And in most clubs the current owner is also paying monthly dues of $50-250, which they will continue to have to pay for every month they don't sell to you.