Well done!
HoP has always been a problem card for me. I disregard it most of the times because I'm rubbish with it and then I get stumped by a creative opponent. 
Highway is certainly a good supercharger for HoP as it is for Workshop, Ironworks (or Feast hehe).
I think when building an engine, it's always worth considering HoP, and often they are good buys. At least one. You should have something to buy for <$5 anyway, because an engine with components all >=$5 is hard to set up. Village, Smithy, Copper, Silver, HoP already is $5, even if you don't find all you should have a target. There should be a payload also, so most of the time the HoP should give you some really nice cards.
It nerfes your purchasing power, put that should also not be a problem, because the HoP itself gives you some $5s, and as said there should be interesting cards even if you don't have much money in hand.
And of course in the end there is should be no problem to get them to $8, Village, Smithy, Copper, Silver, Gold, HoP, Kicker leaves you with one extra card over the cards you anyway want to have in most engines that you have to include.
For pure Cantrip-engines that's of course not so true and you have to look maybe a little more carefully, but for Village/Smithy they are often usefull, and are one of the few cards that can really fully replace the needed +buy for the engine. It helps building up, and it helps scoring.
Edit: For BigMoney, ignore it!
