Forum Moderators: buckworks
On the cheap - plan for about $5k USD unless you do all of the coding. A robust, small shop size, ecommerce venture (not an Amazon but with some of the features of the carts used by the big shops) plan for $50K USD and up.
The better way to approach this, especially if this is your first foray into Ecommerce is to start with a solid, well built, indexable/SEO'd catalog that fits your budget, get's you in the game, and allows you to learn and figure out what you want in the next generation - plan a review and upgrade at about a year out. No one can determine or foresee all of the items they'll want or need a year from now. I recommend my clients pick a good starting point and go with that for a while then review and upgrade after many months or even a year of using it.