Depends of course on how long it is (normally use not steeper than a 1:12 slope - one inch rise foot of run), and a 5'x5' landing top and bottom and at every change of direction or end of run. And you need a level landing every 30" of rise (so as 1:12 slope every 30 feet of ramp run if longer than that).
You said to code - bear in mind some states like California and Massachusetts and NY have modified their ACA compliant codes - CA for instance now requires, as I recall, 48" clear ramp width rather than 36", and 6 foot landings rather than 5 foot, for instance. So be sure what you sink the money into meets local code completely, so come resale timeit can be advertized as having an ADA compliant ramp. Ditto to any other ADA compliant interior features - door widths, cabinet/sink/counter heights, toilet access, accessible shower/toilet, etc.
You did not say if you are looking at a covering over it for weather, heated for snow/ice melting, etc - but common ballpark numbers for ramps on relatively level ground run in the $100-200/LF range including ground prep and railings - and around $25-50/LF for an awning or roof over it though that can vary a lot.
Here is a previous similar question but for treated wood - concrete woulds normally be more expensive because you are talking a lot of concrete to make a wedge-shaped ramp, though in large cities you can sometimes buy hollow precast ones that might come in around the cost of a wood rammp - but still need more subgrade prep than a wood one so generally still more epxensive.
There are also prefab fiberglass and metal ramps available which assemble pretty easily on-site and except for very long runs only need bottom and top anchorage, so can be cheaper in some cases than stick-built wood ramps. And all can come with easily mounted railings, and some have weather cover kits also.