The prices you use aren't even close to my experience with United for upgradeable tickets with miles. I have never purchased a ticket class to Europe I could upgrade.

A majority of my travel is UA from SFO-Europe. Typically from SFO-LHR or AMS a very cheap ticket is in the $400-550 range. The lowest priced upgradeable ticket with miles is typically $1000-1,500+. (Recently fares are lower, but I am basing this on average prices of the past 4 years when I purchased 20+ tickets.)

3 tickets at $500 = 80,000 miles earned = 1 business class ticket redeemed.
On average 1 or 2 one-way complimentary upgrades to business at the check-in desk (without an SWU) for every three roundtrip flights.

4 trips to Europe with 1 guaranteed business class and maybe 2 in business class if I am lucky and 37,500 status miles.

If I chose to upgrade with miles, then $1500 for one paid ticket in H class = 12,500 status miles, 25,000 miles earned, 40,000 miles burned (on the old charts from past two years; 60,000 miles now). One C class trip to Europe and negative mileage balance, and 1/3 of the status miles.

Let's say I could get H class fare for $750 (wishful thinking), then $1,500 = 2 tickets in H class, 25,000 status miles, 50,000 base miles and 80,000 miles burned (again using the old charts, 120,000 miles now). I have a negative balance of 30,000 miles, and less status miles.

That is why I have purchased 20+ cheap economy tickets to Europe and redeemed a lot of miles for business and first class tickets to Europe.

If the other airlines are allowing upgrades at the lower cost booking fares mentioned above, then I need to look into changing my carrier.