Keep in mind that developers tend to stick to what they know. There are so many different content management systems, and each one requires many hours of learning to develop. It is impossible for everyone to specialize in everything. They may nudge you in the direction of what they are most familiar with.
You say that a "Drupal specialist" recommended not using Drupal. If that person is highly knowledgeable about Drupal, you may want to give that opinion some weight.
Here's an example of a site created in Wordpress that has some of the same features you are looking for:
That is quite a bit of money. But in all fairness, you are asking for a lot. An awful lot. You want a forum, tag cloud, photo zoom feature, user database with "want list" features (this alone will cost a few thousand to develop), and of course not the least of your requirements is e-commerce. Then you want a whole bunch of other things. All of this takes hours to develop and costs money.
Sure, you could buy a BMW for that amount of money. But is your BMW going to earn you profits? No. Your BMW is going to lose value as soon as you drive it off the lot. And the more features you add, the more it costs just like your website. BMW prices range from $30,000 to over $100,000. Same thing goes for building a house. Want a marble counter top? That will cost you.
You should have a contract with any developer that clearly lays out your requirements and what will be delivered. As you want a lot of features that other sites don't have, I wouldn't expect someone to have done something exactly the same as your site. Each BMW that rolls off the production line is a copy. That isn't the same for a website, not one with as many features as you want.
Given that we are still in a rough economy, I have to wonder why developers aren't more eager to ink a contract with you. Maybe as mentioned they are testing the waters to see if you are serious or not.
Instead of laying out your requirements and then seeing how much it would cost, why don't you state your budget then see what you can get for your money? Could you do without the tag cloud? There's cost savings right there.
As with any investment, you should forecast how much value it will add then determine if it is worth it. If you could make $150,000 a year in additional profits from your website, $75,000 would be a very reasonable up-front investment.