Need a cost calculator for staircase railing manufacturing and installation

We run a small metalworking workshop that manufactures and installs staircase railings and balustrades for private houses, offices and commercial buildings, and right now every price request goes through a manager who calculates the cost by hand over the phone or in a messenger. Many of those leads simply disappear because people don't want to wait for a callback and move on to a competitor who shows a number right away, so we want an online calculator embedded on our website that gives an instant estimate.

The calculator should let the visitor set the length and height of the railing, choose the material (metal balusters, wood, tempered glass, or a combination), select the pattern complexity, from plain straight bars to ornate wrought designs, pick the handrail type, and specify whether the installation is indoor or outdoor, on a staircase, porch or balcony. Based on these it should compute a final price, ideally as a range, plus an estimated production and installation timeframe, then invite the visitor to leave contact details for a precise quote.

What we need built:
— a step-by-step configurator with the price updating live
— pricing coefficients per material and complexity we can edit ourselves
— a mobile-friendly layout matching the existing site
— a simple settings panel or config file for base rates