The demo running fine and i didn't experience any problem. But as @dkbit98 said, the UI definitely need some improvement. For example, i find exchange rate "1 Sat = 1 Sats" is pointless. It should be hidden if the owner using satoshi as default currency unit.
Price for website integration is €249 and I think that can be reduced or maybe you could add several tier packages with lower prices.
IMO, it's acceptable price for premium support/service since the base product/support is totally free. Although i wonder how many people would pay for 249 EUR.