Fighting back against supermarkets

Yet again, another example of tesco and asda identical pricing in our area, where they both have stores close to each other.

Nescafe coffee 300g jars:
- Both asda and tesco put their prices up to more than £6 per jar (within 2p of each other)
- Both asda and tesco then reduce them to £4 on offer (at the same time)
- Both asda and tesco then increase them back up to more than £6 (again at the same time, again within 2p of each other)
- Three weeks go by, both asda and tesco keep them at the more than £6 in price
- As if by magic, the price is reduced to an offer price of £5, by both asda and tesco, on the same day!

Lurpak:
- Both asda and tesco selling it for £1.38
- Both asda and tesco increase the individual pack price to £1.50 (on the same day)

Examples of same day increases in prices and identical offers going on come up every week. How is this not a supermarket monopoly?