You can get an Amex that's not a platinum card for way less than $450. That's a big nut but the big benefit like i said is access to the airline lounges. You get into American, Delta & US Air (not sure bout United). The cost is around $450 each if you were to buy them individually.
If you get a green card from Amex, I think the fee is like $75.00 a year. Then the fee to join membership rewards is $25.00 - i think that's a one time fee. You can earn the same # of points, etc on an Amex green as the Plat card, so you can get the cost way down.
From what I've seen the best way to compare cards is to equate one point to be equal to one cent. Thus if you did amex green at $75.00 a year, you would have to charge at least $7,500 a year on the card to break even. After that it's just money back for you. On my business it means a ton of points for me, and it's really worth it (plus Amex has given my business a very favorable line of credit, so I'm able to buy time with no interest charges associated with it- another huge plus for me).
The other plus you'll see with Amex is that they will run specials, where you get a bonus for transfering your membership rewards points in any given month of up to 40% .... so, 10,000 rewards points can turn into 14,000 miles. In my case, 100,000 Amex Rewards points turns into 140,000 miles, so instead of getting 4 free round trip tickets I end up getting 5 free round trip tickets (25,000 miles each) and then have another 15,000 points left over.
Most airlines start a domestic round trip ticket at 25,000 miles and go up from there. Domestic First Class is around 40,000 miles.
Hotels vary greatly. Marriott Rewards has category's for their hotels
1 night at a category 1 hotel (think fairfield inn) is 7,500 points
1 night at a category 2 hotel is 10,000 points
all the way up to
1 night at a category 8 hotel is 40,000 points (think ritz carlton on Hawaii)
If you're looking for hotel rewards, Chase has a Marriott Rewards Visa card, which gives:
22,500 points with first spend
1 free night stay (not sure which category)
3 points for every $ spent at a Marriott hotel
1 point for every $ spent elsewhere
Elite Status (only Silver but it's better than nothing)
10 nights credit towards higher elite status
for every $3k spent another night credit towards elite status
Lastly, if you build up enough points to take a 7 night stay, you get 15,000 points refunded after the stay is completed.