The wife and I have been popping E's nearly ever weekend for the past 15 years. Don't think they have done us any harm. We do get comedowns & feel a bit rough, but only when we have done 2 or 3 nights on the trot.
When I first started I was paying £10 a go, lowest the price got was around £1.50, but over the last couple of years price has started rising again to around £5 or £6. I think this is because its become less popular and more difficult for us to get hold of.
Was paying 3e in Ibiza two years ago, but this year 6e. May have just got ripped off I suppose.
As for quality dont really think it has varied much over the 15 years....sometimes there good sometimes not.
Don't really do anything other than E, so can't comment on the legal highs or other gear.